4-Acylthioazetidinone intermediates for antibacterial agents

ABSTRACT

This invention relates to 2-substituted and 2,6-disubstituted penem compounds of the formula ##STR1## wherein Y is hydrogen, halo or certain organic radicals and X represents certain hetero-interrupted substituted alkyl radicals. Also included in the invention are pharmaceutically acceptable salts of the above compounds and derivatives of the above compounds in which the carboxyl group at the 3-position is protected as by an easily removable ester protecting group. The compounds of the present invention are potent antibacterial agents or are of use as intermediates in the preparation of such agents.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of co-pending Ser. No. 253,982 filedApr. 13, 1981 U.S. Pat. No. 4,406,834 which is a divisional of Ser. No.77,886 filed Sept. 21, 1979 is Pat. No. 4,282,150 which in turn was acontinuation-in-part application of Ser. No. 968,663 filed Dec. 18, 1978and now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Novel 2-substituted and 2,6-disubstituted penem compounds are preparedby totally synthetic chemical processes and found to be potent β-lactamantibiotics.

2. Description of the Prior Art

Penicillins and cephalosporins comprise a group of well-knownantibacterial agents commonly grouped together as a class calledβ-lactam antibiotics. Most of the work in this field has been done,broadly speaking, with 6-aminopenicillanic acid (6-APA),7-aminocephalosporanic acid (7-ACA) and derivatives thereof produced byfermentation or chemical transformation of the natural products. Despitethe extensive progress made in preparing active derivatives of 6-APA and7-ACA, there is a continuing search for synthetic and semi-syntheticroutes to new families of β-lactam antibiotics which may possess moreadvantageous properties than those derived from the known penicillin andcephalosporin nuclei.

Considerable work has been done on total chemical synthesis of bothknown β-lactams and nuclear analogs of such known compounds. Literaturepublications relating to non-conventional bicyclic β-lactams include thefollowing:

(a) Belgian Patent No. 846,933 discloses the compound of the formula##STR2## which has been isolated from fermentation of Streptomycesclavuligerus. This compound, named clavulanic acid, possesses a loworder of antibacterial activity but inhibits the action of certainβ-lactamases and reportedly enhances the in vitro and in vivo activityof some penicillins and cephalosporins.

(b) U.K. Pat. No. 1,467,413 discloses the fermentation product havingthe formula ##STR3## which is reported to possess some antibacterialactivity and to be a β-lactamase inhibitor.

(c) Brown, et al. in J.C.S., Chem. Comm., 359-360 (1977) disclosepreparation of the compound of the formula ##STR4## There is noindication from the publication that the compound possesses anyantibacterial activity.

(d) Eglington in J.C.S. Chem. Comm., 720 (1977) discloses preparation ofthe ester of the formula ##STR5## The compound is reported to be a weakinhibitor of β-lactamases.

(e) U.S. Pat. No. 3,950,357 describes a fermentation process forproducing thienamycin, the compound of the formula ##STR6## Thienamycinis reported to be a highly potent broad-spectrum antibiotic.

(f) Belgian Pat. No. 849,118 (equivalent U.S. is U.S. Pat. No.4,118,566) discloses a series of 6-amino-2-penem-3-carboxylic acidderivatives of the formula ##STR7## wherein R₁ ^(a) is hydrogen or anN-protecting group, R₁ ^(b) is hydrogen or acyl (or R₁ ^(a) and R₁ ^(b)taken together are a divalent N-protecting group), --CO--R₂ is carboxylor a protected carboxyl group and R₃ is hydrogen or a C-bonded organicgroup. The compounds and their salts are said to possess antibacterialactivity. No compounds are disclosed which do not contain the amino oracylamido moiety at the 6-position of the β-lactam ring.

(g) Acta Pharmaceutica Suecica, 14 (Suppl.), 23-25 (1977) discloses2,6-disubstituted penems of the formula ##STR8## and reports such penemsto be considerably less active than the penicillin and cephalosporinanalogs. Also disclosed as antibacterial agents (again withoutdefinition of R) are 2-substituted penems of the formula ##STR9##

(h) Annual Reports in Medicinal Chemistry, 13, 239-248 (1978) disclosesthe unsubstituted penem of the formula ##STR10## as having noβ-lactamase inhibitory activity.

(i) South African Pat. No. 77/6594 discloses1-carba-2-penem-3-carboxylic acids of the formula ##STR11## wherein R¹,R² and R³ are independently selected from the group consisting ofhydrogen, substituted and unsubstituted: alkyl, alkenyl, cycloalkyl,cycloalkylalkyl, alkylcycloalkyl, aryl, aralkyl, aralkenyl, aralkynyl,heteroaryl, heteroaralkyl, heterocycyl and heterocycylalkyl wherein thesubstituent or substituents relative to the above-named radicals areselected from the group consisting of amino, hydroxy, alkoxyl, mercapto,alkylthio, arylthio, sulfamoyl, amidino, guanidino, nitro, chloro,bromo, fluoro, cyano and carboxy and wherein the hetero atom in theabove-named heterocyclic moiety is selected from the group consisting ofoxygen, nitrogen and sulfur. The compounds are reported to haveantibiotic activity.

(j) Belgian Pat. No. 866,845 discloses 2-penem compounds of the formula##STR12## wherein R₁ =hydrogen or an organic radical (bonded to the ringcarbon atom via a carbon atom) or an etherified mercapto group and R₂ ishydrogen or a group R₂ ^(A) which forms with CO a protected carboxylicgroup. The disclosed compounds are reported to be antibacterial agentsand β-lactamase inhibitors.

SUMMARY OF THE INVENTION

The present invention provides certain novel 2-substituted and2,6-disubstituted penem compounds which possess potent antibioticactivity. Also provided are various novel intermediates useful inpreparing the biologically active penem derivatives and variousprocesses for the production of the intermediates and active compounds.

The penem ring system has the formula ##STR13## and systematically canbe designated as 7-oxo-4-thia-1-azabicyclo[3.2.0]hept-2-ene. For thesake of simplicity, it is named "2-penem" in the present application andthe numbering system used is as follows: ##STR14##

There is thus provided by the present invention the novel2,6-disubstituted penems having the formula ##STR15## wherein Z ishydrogen or an easily cleavable ester protecting group; Alk represents aC₁ -C₂ alkylene group optionally substituted by a C₁ -C₄ alkyl radical;A is O, S, SO, SO₂ or NR₂₁ in which R₂₁ is hydrogen, (lower)alkyl,phenyl or phenyl(lower)alkyl; Alk' is a C₂ -C₄ alkylene group; R₂₀ is apolar substituent selected from the group consisting of --NHOH, --NR₂₂R₂₃ in which R₂₂ and R₂₃ are each independently hydrogen or (lower)alkyland --NO₂ ; and Y is hydrogen or a radical selected from the groupconsisting of

(a) optionally substituted (lower)aliphatic, (lower)cycloaliphatic or(lower)cycloaliphatic(lower)aliphatic, the substituents being one ormore of hydroxy, (lower)alkoxy, optionally substituted phenyloxy,optionally substituted heterocyclicoxy, optionally substituted(lower)alkylthio, optionally substituted phenylthio, optionallysubstituted heterocyclicthio, mercapto, amino, (lower)alkylamino,di(lower)alkylamino, (lower)alkanoyloxy, (lower)alkanoylamino,optionally substituted phenyl, optionally substituted heterocyclic,carboxy, carb(lower)alkoxy, carbamoyl, N-(lower)alkylcarbamoyl,N,N-di(lower)alkylcarbamoyl, halo, cyano, oxo, thioxo, --SO₃ H, --OSO₃H, --SO₂ --(lower)alkyl, (lower)alkylsulfinyl, nitro, phosphono or##STR16## in which R_(e) and R_(r) are as defined above, thesubstitutents on the (lower)alkylthio group being one or more of halo,hydroxy, (lower)alkoxy, amino, (lower)alkanoylamino or optionallysubstituted phenyl or heterocyclic and the phenyl or heterocyclicsubstituents above being one or more of hydroxy, (lower)alkoxy, halo,(lower)alkyl, halo(lower)alkyl, methanesulfonyl, (lower)alkylthio,amino, (lower)alkanoylamino, (lower)alkanoyloxy, carboxy,carboxy(lower)alkyl, sulfo or sulfo(lower)alkyl;

(b) --OR_(s) in which R_(s) is optionally substituted (lower)alkyl or(lower)alkanoyl or optionally substituted phenyl or heterocyclic, thesubstituents on the alkyl and alkanoyl being one or more of halo,hydroxy, (lower)alkoxy, (lower)alkylamino, di(lower)alkylamino, amino,oxo, (lower)alkanolyamino or optionally substituted phenyl orheterocyclic and the substituents on the phenyl or heterocyclic beingone or more of hydroxy, (lower)alkoxy, halo, (lower)alkyl,halo(lower)alkyl, methanesulfonyl, (lower)alkylthio, (lower)alkylamino,di(lower)alkylamino, amino, (lower)alkanoylamino, (lower)alkanoyloxy,carboxy, carboxy(lower)alkyl, sulfo or sulfo(lower)alkyl;

(c) --SO(O)_(n) R_(s) in which n is 0, 1 or 2 and R_(s) is as definedabove;

(d) halo; and

(e) optionally substituted phenyl or heterocyclic in which thesubstituents are one or more of hydroxy, (lower)alkoxy, halo,(lower)alkyl, halo(lower)alkyl, methanesulfonyl, (lower)alkylthio,amino, (lower)alkylamino, di(lower)alkylamino, (lower)alkanoylamino,(lower)alkanoyloxy, carboxy, carboxy(lower)alkyl, sulfo orsulfo(lower)alkyl; or a pharmaceutically acceptable salt thereof.

The compounds of formula I wherein Z is hydrogen (and theirpharmaceutically acceptable salts and physiologically hydrolyzed esters)are potent antibacterial agents. The remaining compounds are usefulintermediates for preparation of the biologically active penems.

Substituent groups disclosed above for the 2- and 6-positions of thepenem ring may be further defined as follows:

(a) Halo includes chlorine, bromine, fluorine and iodine. Preferred halosubstituents are chlorine and fluorine;

(b) (Lower)alkyl includes both straight and branched chain saturatedaliphatic hydrocarbon radicals having from 1-6 carbon atoms inclusive,e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl,tert-butyl, n-pentyl, isopentyl, n-hexyl, etc. Preferred (lower)alkylsubstituents have from 1-4 carbons and most preferably 1-2 carbons;

(c) (Lower)aliphatic is intended to include acyclic straight andbranched chain saturated and unsaturated hydrocarbon radicals havingfrom 1-6 carbon atoms inclusive. The unsaturated radicals may containone or more double or triple bonds, but preferably contain either onedouble bond or one triple bond. Examples of (lower)aliphatic are methyl,ethyl, n-propyl, isopropyl, n-butyl, t-butyl, sec-butyl, n-pentyl,isobutyl, vinyl, 1-propenyl, 2-propenyl, isopropenyl,2-methyl-2-propenyl, ethynyl and 2-propynyl. The most preferredaliphatic radicals are (lower)alkyl as in (b);

(d) (Lower)cycloaliphatic is intended to represent alicyclic saturatedand unsaturated hydrocarbon radicals having from 3-8 ring carbon atoms,preferably 3-6 carbon atoms. The unsaturated ring may contain one ormore (preferably one) double bond. Examples of this group includecyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl,cyclooctyl, cyclopropenyl, cyclopentenyl, 1,3-cyclohexadienyl andcyclohexenyl;

(e) (Lower)cycloaliphatic(lower)aliphatic representscycloaliphatic-aliphatic radicals having 3-8 carbon atoms (preferably3-6) in the cycloaliphatic ring and 1-6 carbon atoms (preferably 1-4 andmost preferably 1-2) in the aliphatic portion. Examples includecyclopropylmethyl, cyclopropylethyl, cyclopropylpentyl, cyclobutylethyl,cyclopentylmethyl, cyclohexylmethyl, cyclopropenylmethyl,cyclopentenylethyl, cyclopropylethenyl, cyclopropylethynyl, etc. Themost preferred radicals of this type are cycloalkyl-alkyl in which thecycloalkyl portion contains 3-6 carbons and the alkyl portion contains1.2 carbons;

(f) (Lower)alkoxy includes C₁ -C₆ alkoxy radicals, the alkyl portion ofwhich being defined as in (b). Examples include methoxy, ethoxy,n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, n-pentyloxy,etc. Preferred are C₁ -C₄ alkoxy and most preferred are C₁ -C₂ alkoxy;

(g) (Lower)alkylthio includes C₁ -C₆ alkylthio radicals in which thealkyl portion is as defined under (b). Examples include methylthio,ethylthio and n-butylthio;

(h) (Lower)alkylamino includes C₁ -C₆ alkylamino radicals in which thealkyl portion is as under (b). Examples are methylamino, ethylamino,n-propylamino and n-butylamino;

(i) Di(lower)alkylamino represents di C₁ -C₆ alkylamino in which eachalkyl is as defined under (b). Examples are dimethylamino anddiethylamino;

(j) (Lower)alkanoyloxy represents radicals of the formula ##STR17## inwhich alkyl is as defined under (b); (k) (Lower)alkanoylamino includesradicals of the formula ##STR18## in which alkyl is as under (b); (l)Carb(lower)alkoxy represents ##STR19## in which (lower)alkoxy is asunder (f); (m) Halo(lower)alkyl represents alkyl radicals in which oneor more hydrogen atoms are replaced by a halogen atom;

(n) Sulfo(lower)alkyl represents --(CH₂)_(n) SO₃ H in which n is 1-6;

(o) Carboxy(lower)alkyl represents --(CH₂)_(n) COOH in which n is 1-6;

(p) Phenyl(lower)alkyl represents ##STR20## in which n is 1-6; (q)(Lower)alkanoyl represents ##STR21## in which alkyl is as under (b); (r)N-(Lower)alkylcarbamoyl represents ##STR22## in which alkyl is as under(b); (s) N,N-Di(Lower)carbamoyl represents ##STR23## in which each alkylis as under (b); (t) (Lower)alkylsulfinyl represents ##STR24## in which(lower)alkyl is as defined above under (b).

The term "heterocyclic" as used herein is intended to includeheteromonocyclic and heterobicyclic residues of aromatic character aswell as appropriate partially or wholly saturated residues, saidheterocyclic residues containing at least one heteroatom selected fromoxygen, sulfur and nitrogen and being bonded to the penem ring carbonatom via a ring carbon atom. The preferred heterocyclic groups areeither 5- or 6-membered monocyclic radicals or fused 6,6 or 5,6 bicyclicradicals. Illustrative of suitable heterocyclic radicals are thefollowing: ##STR25## Similarly, the terms heterocyclic-(lower)alkyl,heterocyclicthio-(lower)alkyl, heterocyclicoxy and heterocyclic-thiorepresent --(CH₂)_(n) --Heterocyclic, --(CH₂)_(n) --S--Heterocyclic,--O--Heterocyclic and --S--Heterocyclic, respectively, in which n is 1-6(preferably 1 or 2).

Since an asymmetric carbon atom is present in the 2-substitutedcompounds of formula I, such compounds may exist either in the form ofracemic mixtures (R,S form) or as the individual dextrorotatory andlevorotatory (R- and S-forms) optical isomers. Preferred are thecompounds in which the configuration of the 5-carbon atom corresponds tothat of natural penicillin (5R-configuration). Substituents at the 5-and 6-positions of the 2,6-disubstituted penems may be in the cis ortrans position in relation to one another. Where the penem 6-substituentcontains an asymmetric carbon atom, the resulting isomers are identifiedherein as isomers A, B, C and D (see Example 5 for stereochemistry). Thepreferred isomer in compounds of this type is isomer B. Separation ofthe various optical and geometric isomers may be carried out byconventional separation and resolution procedures well-known to thoseskilled in the art.

The present invention is intended to include the compounds of formula Iin the form of isomer mixtures and also in the form of the individualseparated and resolved isomers.

The pharmaceutically acceptable salts referred to above include thenontoxic carboxylic acid salts, e.g. nontoxic metallic salts such assodium, potassium, calcium, aluminum and magnesium, the ammonium saltand salts with nontoxic amines such as trialkylamines (triethylamine),procaine, dibenzylamine, N-benzyl-β-phenethylamine, 1-ephenamine,N,N'-dibenzylethylenediamine, N-alkylpiperidine and other amines whichhave been used to form salts of penicillins and cephalosporins. When abasic group is present, the present invention also includes thepharmaceutically acceptable acid addition salts, e.g. salts with mineralacids such as hydrochloric, hydrobromic, hydroiodic, phosphoric,sulfuric or with suitable organic carboxylic acids or sulfonic acidssuch as trifluoroacetic, p-toluenesulfonic, maleic, acetic, citric,oxalic, succinic, benzoic, tartaric, fumaric, mandelic, ascorbic andmalic. Compounds containing an acid group and a basic group can also bein the form of inner salts, i.e. a zwitterion. Preparation of theabove-described salts may be carried out according to conventionalprocedures for forming salts of β-lactam antibiotics such as penicillinsand cephalosporins.

The term "easily removable ester protecting group" is one which hasacquired a definite meaning within the β-lactam and peptide art. Manysuch groups are known which are used to protect the carboxyl groupduring subsequent chemical reactions and which may later be removed bystandard methods to give the free carboxylic acid. Known esterprotecting groups include 2,2,2-trichloroethyl, tertiary alkyl of from4-6 carbon atoms, tertiary alkenyl of from 5-7 carbon atoms, tertiaryalkynyl of from 5-7 carbon atoms, alkoxymethyl, alkanoylmethyl of from2-7 carbon atoms, N-phthalimidomethyl, benzoylmethyl, halobenzoylmethyl,benzyl, p-nitrobenzyl, o-nitrobenzyl, benzhydryl, trityl,trimethylsilyl, triethylsilyl, β-trimethylsilylethyl, and the like.Choice of an ester protecting group is dependent on the subsequentreaction conditions the group must withstand and the conditions desiredfor removing it. Selection of a suitable group is well within theability of one skilled in the art. For use as a chemical intermediatethe most preferred ester is the p-nitrobenzyl ester which can be readilyremoved by catalytic hydrogenation. For preparation of compoundscontaining functional groups reducible under such removal conditions, apreferred alternative is the β-trimethylsilylethyl ester removable bytreatment with fluoride ions. Also included within the scope of easilyremovable ester protecting groups are physiologically cleavable esters,i.e. those esters known in the penicillin and cephalosporin art to beeasily cleaved within the body to the parent acid. Examples of suchphysiologically cleavable esters include indanyl, phthalidyl,methoxymethyl, glycyloxymethyl, phenylglycyloxymethyl,thienylglycyloxymethyl or acyloxymethyl of the formula ##STR26## inwhich Y' is C₁ -C₄ alkyl or phenyl. Particularly preferred esters ofthis type are methoxymethyl, acetoxymethyl, pivaloyloxymethyl,phthalidyl and indanyl.

It will be appreciated that the compounds of formula I may exist invarious states of solvation and the anhydrous as well as solvated(including hydrates) forms are intended to be within the scope of theinvention.

With respect to the compounds of formula I, the preferred compounds arethose wherein Y is hydrogen or (lower)alkyl optionally substituted(preferably at the α-carbon) by hydroxy. More preferred compounds withinthe above group are those wherein Y is hydrogen, ethyl orα-hydroxyethyl. Still more preferred compounds of formula I are thosewherein Y is hydrogen or α-hydroxyethyl. The most preferred compoundsare those wherein Y is α-hydroxyethyl.

A preferred embodiment of the present invention consists of thecompounds of formula I wherein the 2-substituent is

    --(Alk)--O--(Alk')--R.sub.20

in which Alk, Alk' and R₂₀ are as defined above. Examples ofsubstituents included within this class include --CH₂ OCH₂ CH₂ NH₂,--CH₂ CH₂ OCH₂ CH₂ NH₂, --CH₂ OCH₂ CH₂ NHCH₃, --CH₂ OCH₂ CH₂ N(CH₃)₂,--CH₂ OCH₂ CH₂ NHC₂ H₅, --CH₂ OCH₂ CH₂ N(C₂ H₅)₂, --CH₂ OCH₂ CH₂ NHC₃H₇, --CH₂ OCH₂ CH₂ N(C₃ H₇)₂, --CH₂ OCH₂ CH₂ CH₂ NH₂, --CH₂ OCH₂ CH₂ CH₂CH₂ NH₂, --CH₂ OCH₂ CH₂ CH₂ CH₂ NHCH₃, --CH₂ OCH₂ CH₂ CH₂ CH₂ N(CH₃)₂,--CH₂ CH₂ OCH₂ CH₂ NHCH₃, --CH₂ CH₂ OCH₂ CH₂ N(CH₃)₂ , --CH₂ CH₂ OCH₂CH₂ CH₂ NH₂, --CH₂ CH₂ OCH₂ CH₂ CH₂ NHCH₃, --CH₂ CH₂ OCH₂ CH₂ CH₂N(CH₃)₂, ##STR27## --CH₂ OCH₂ CH₂ NHOH, --CH₂ OCH₂ CH₂ CH₂ NHOH, --CH₂CH₂ OCH₂ CH₂ NHOH, --CH₂ OCH₂ CH₂ NO₂, --CH₂ OCH₂ CH₂ CH₂ CH₂ NO₂, --CH₂CH₂ OCH₂ CH₂ NO₂, ##STR28## and --CH₂ OCH₂ CH₂ CH₂ CH₂ NHOH. Within thisclass of compounds, the preferred members are those wherein Y ishydrogen, ethyl or α-hydroxyethyl. Most preferred members haveY=hydrogen or α-hydroxyethyl and especially Y=α-hydroxyethyl.

Another preferred embodiment of the present invention consists of thecompounds of formula I wherein the 2-substituent is

    --(Alk)--S--(Alk')--R.sub.20

in which Alk, Alk' and R₂₀ are as defined above. Examples ofsubstituents within this class include --CH₂ SCH₂ CH₂ NH₂, --CH₂ CH₂SCH₂ CH₂ NH₂, --CH₂ SCH₂ CH₂ CH₂ NH₂, --CH₂ SCH₂ CH₂ CH₂ CH₂ NH₂, --CH₂SCH₂ CH₂ NHCH₃, --CH₂ SCH₂ CH₂ N(CH₃)₂, --CH₂ SCH₂ CH₂ NHC₂ H₅, --CH₂SCH₂ CH₂ N(C₂ H₅)₂, --CH₂ SCH₂ CH₂ NHC₄ H₉, --CH₂ SCH₂ CH₂ N(C₄ H₉)₂,--CH₂ SCH₂ CH₂ CH₂ NHCH₃, --CH₂ SCH₂ CH₂ CH₂ N(CH₃)₂, --CH₂ SCH₂ CH₂ CH₂N(C₃ H₇)₂, --CH₂ SCH₂ CH₂ CH₂ CH₂ NHCH₃, --CH₂ CH₂ SCH₂ CH₂ CH₂ NH₂,--CH₂ CH₂ SCH₂ CH₂ NH₂, ##STR29## --CH₂ SCH₂ CH₂ NHOH, --CH₂ SCH₂ CH₂CH₂ NHOH, --CH₂ SCH₂ CH₂ CH₂ CH₂ NHOH, --CH₂ CH₂ SCH₂ CH₂ NHOH, --CH₂CH₂ SCH₂ CH₂ CH₂ NHOH, ##STR30## --CH₂ SCH₂ CH₂ NO₂, --CH₂ SCH₂ CH₂ CH₂NO₂, --CH₂ SCH₂ CH₂ CH₂ CH₂ NO₂, --CH₂ CH₂ SCH₂ CH₂ NO₂ and --CH₂ CH₂SCH₂ CH₂ CH₂ NO₂. Within this class of compounds, the preferred membesare those wherein Y is hydrogen, ethyl or α-hydroxyethyl. Most preferredmembers have Y=hydrogen or α-hydroxyethyl and especiallyY=α-hydroxyethyl.

An especially preferred embodiment of the present invention consists ofthe following compounds included within formula I:

(a) Y=H; 2--CH₂ OCH₂ CH₂ NH₂ ;

(b) Y=α-hydroxyethyl; 2--CH₂ OCH₂ CH₂ NH₂ ;

(c) Y=H; 2--CH₂ OCH₂ CH₂ NHOH;

(d) Y=α-hydroxyethyl; 2--CH₂ OCH₂ CH₂ NHOH;

(e) Y=H; 2--CH₂ SCH₂ CH₂ NH₂ ;

(f) Y=α-hydroxyethyl; 2--CH₂ SCH₂ CH₂ NH₂ ;

(g) Y=H; 2--CH₂ SCH₂ CH₂ NHOH;

(h) Y=α-hydroxyethyl; 2--CH₂ SCH₂ CH₂ NHOH; ##STR31## (m) Y=H; 2--CH₂OCH₂ CH₂ NO₂ ; (n) Y=α-hydroxyethyl; 2--CH₂ OCH₂ CH₂ NO₂ ;

(o) Y=H; 2--CH₂ SCH₂ CH₂ NO₂ ;

(p) Y=α-hydroxyethyl; 2--CH₂ SCH₂ CH₂ NO₂ ; ##STR32## Especiallypreferred are the above-described compounds where Z in formula I ishydrogen, pharmaceutically acceptable salts thereof and physiologicallycleavable esters thereof such as acetoxymethyl, methoxymethyl,pivaloyloxymethyl, phthalidyl and indanyl.

Most preferred compounds of the present invention are those whereY=hydrogen or, more preferably, α-hydroxyethyl, and the 2-substituent is--CH₂ OCH₂ CH₂ NH₂, most especially the free acids, pharmaceuticallyacceptable salts thereof and physiologically cleavable esters thereof.

In another aspect the present invention comprises novel intermediates ofthe formula ##STR33## wherein Y is as defined above in regard tocompounds of formula I, Q is phenyl or (lower)alkyl, R" is an easilyremovable ester protecting group and T is ##STR34## wherein X is--(Alk)--A--(Alk')--R₂₀.

In the intermediates of formula II, Q is preferably phenyl, R" ispreferably p-nitrobenzyl and X and Y are preferably those substituentgroups mentioned as being preferred in connection with the compounds offormula I. Reactive functional groups such as mercapto, amino andhydroxy in substituents X and Y may be protected by conventionalblocking grops during conversion of the intermediates to biologicallyactive end-products. For example, R₂₀ in intermediate II may be --N₃which on catalytic hydrogenation will be converted to a free aminogroup.

Compound I may be prepared by one or more of the reaction routesdiscussed below. The various synthetic routes may be divided into threemain processes depending on the stage of incorporation of the6-substituent, i.e. Y. Thus, in Process I, the 6-substituent isincorporated in the basic starting material; Process II involvesincorporation of Y at the end of the synthesis and in Process IIIsubstituent Y is incorporated in mid-synthesis. Each of the three mainprocesses in turn can vary in the procedure for incorporating thedesired 2-substituent, i.e. X in the schemes shown below. In general, itis preferred to incorporate substituent Y in mid-synthesis and toincorporate substituent X by acylation of the mercaptide intermediatesIII or III_(a) shown below since these procedures have been found to bethe most generally useful.

The steps of Process I may be seen from the following scheme: ##STR35##

In Process I a vinyl ester (Y=H or a radical as defined in connectionwith compounds I) containing the desired 6-substituent is converted tothe optionally 1-substituted 4-acetoxy-2-azetidinone by a cycloadditionreaction with chloro sulfonyl isocyanate (CSI) followed by reductionwith an organic reducing agent such as sodium sulfite. The CSI reactionis conveniently carried out in an inert organic solvent such as diethylether at a temperature of 0° C. or below. The reduction step may beconducted in an aqueous or aqueous-organic reaction mixture at atemperature of 0° or below and at a slightly basic pH.

Following formation of the 4-acetoxy-2-azetidinone, Process I may beseparated into three different paths. In one route (Variation 1) theazetidinone is reacted with a thiolic acid ##STR36## wherein X is asdefined in connection with compounds I, or a salt thereof, in a suitablesolvent (e.g. aqueous or aqueous organic). Displacement of the acetoxygroup results in incorporation of the desired 2-substituent in theazetidinone at this stage. The displacement reaction is preferablycarried out at room temperature or below and at a slightly basic pH(˜7.5). When Y≠H, cis and trans isomers of the resulting azetidinone arepreferably separated (e.g. by chromatography) at this point in theprocess. Variations 2 and 3 depicted above convert the4-acetoxy-2-azetidinone into the 4-acetylthio-2-azetidinone and4-tritylthio-2-azetidinone products, respectively, by nucleophicdisplacement with thioacetic acid or triphenylmethyl mercaptan (or asalt thereof such as the sodium salt), respectively.

The 4-thio azetidinone is next reacted with a glyoxylate ester ##STR37##wherein R" is an easily removable ester protecting group such asp-nitrobenzyl or trimethylsilylethyl, or a reactive oxo derivativethereof such as a hydrate, in an inert organic solvent (e.g. benzene,toluene, xylene, and the like) and preferably at an elevated temperature(e.g. 50° C. up to most preferably reflux temperature). When a hydrateof the ester is employed, resulting water may be removed azeotropicallyor with molecular sieves. The hydroxy ester product is formed as amixture of epimers which can be optionally purified as by chromatographyor used directly in the next step.

Conversion of the hydroxy ester to the corresponding chloro ester isachieved by reaction with a chlorinating reagent (e.g. SOCl₂, POCl₃,PCl₅, and the like) in an inert organic solvent (e.g. tetrahydrofuran,diethyl ether, methylene chloride, dioxane, and the like) in thepresence or absence of a base, preferably an aliphatic tertiary amine(e.g. triethylamine) or a heterocyclic tertiary amine (e.g. pyridine orcollidine). The reaction is advantageously run at from about -10° C. toroom temperature. Chloro ester product is obtained as a mixture ofepimers which can optionally be purified before use in the next step.

The phosphorane intermediate may be obtained by reaction of the chloroester with a suitable phosphine (preferably triphenylphosphine or atri(lower)alkyl phosphine such as triethylphosphine or tri-n-butylphosphine) in an inert organic solvent such as dimethylformamide,dimethylsulfoxide, tetrahydrofuran, dimethoxyethane, dioxane or analiphatic, cycloaliphatic or aromatic hydrocarbon (e.g. hexane,cyclohexane, benzene, toluene, and the like) in the presence of a base,preferably an organic tertiary amine such as triethylamine, pyridine or2,6-lutidine. The reaction is advantageously carried out at temperaturesfrom room temperature to the reflux temperature of the solvent system.

At this stage the process again diverges into two routes. In Variation I(where the 2-substituent has already been incorporated), the phosphoraneintermediate is converted to the desired penem by thermally cyclizing inan inert organic solvent at a temperature of from just above roomtemperature to the reflux temperature of the solvent system. Mostconveniently, the cyclization is carried out under reflux conditions.Suitable inert organic solvents include aliphatic, cycloaliphatic oraromatic hydrocarbons (e.g. benzene, toluene, hexane, cyclohexane),halogenated hydrocarbons (e.g. methylene chloride, chloroform, carbontetrachloride), ethers (diethyl ether, dioxane, tetrahydrofuran,dimethoxyethane), carboxylic acid amides (e.g. dimethylformamide), di C₁-C₆ alkylsulfoxides (e.g. dimethylsulfoxide) or a C₁ -C₆ alkanol (e.g.methanol, ethanol, t-butanol), or a mixture thereof.

In variations 2 and 3 the phosphorane is converted to a heavy metalmercaptide of the formula ##STR38## wherein Y is as defined above withrespect to compounds of formula I, R" is an easily removable estergroup, Q is preferably phenyl or (lower)alkyl, x is 1 or 2 and M isCu(II), Pb(II) or Hg(II) when x is 2 or Ag(I) when x is 1. Mercaptideformation is accomplished by reaction of the phosphorane with a salt ofHg(II), Pb(II), Cu(II) or Ag(I) or with (methoxycarbonyl)mercury(II)acetate in a methanol-containing solvent and in the presence of anorganic or inorganic base such as aniline, pyridine, collidine,2,6-lutidine, an alkali metal carbonate, and the like. A preferred baseis pyridine. The reaction may be carried out at room temperature or, ifdesired, with moderate cooling or heating. The anion (A) of the heavymetal salt may be any anion which gives a soluble salt in the selectedsolvent, e.g. NO₃ ⁻, CH₃ COO⁻, BF₄ ⁻, F⁻, ClO₄ ⁻, NO₂ ⁻, CNO⁻, etc. Themercaptide intermediate is then reacted with an acylating agent capableof introducing the moiety ##STR39## wherein X is the desired penem2-substituent. The acylating agent ##STR40## may be the acid ##STR41##or a reactive functional derivative thereof such as an acid halide(preferably acid chloride), acid azide, acid anhydride, mixed acidanhydride, active ester, active thioester, etc. Acylation is conductedin an inert solvent (e.g. a halogenated hydrocarbon such as methylenechloride or an ether such as dioxane, tetrahydrofuran or diethyl ether)and, when an acid derivative is used, in the presence of an acidacceptor such as a tri(lower)alkylamine (e.g. triethylamine) or atertiary organic base such as pyridine, collidine or 2,6-lutidine. Whenthe free acid is employed, the acylation is conducted in the presence ofa suitable condensing agent, for example a carbodiimide such asN,N'-dicyclohexylcarbodiimide. Acylation of the mercaptide can beachieved over a wide temperature range, but is preferably carried outfrom about -20° to +25° C. Following acylation, the resultingphosphorane is cyclized as described above to give the desired penemester.

Formation of the phosphorane via the mercaptide intermediate (Variations2 and 3) has been found to result in product of much better purity thanthat obtained by the more conventional route of Variation 1.

Once the carboxyl-protected penem is formed, the protecting group may beremoved by conventional de-blocking procedures (e.g. hydrolysis,hydrogenation or photolysis) to give the de-blocked penem. Removal ofthe p-nitrobenzyl ester, for example, may be achieved by catalytichydrogenation in the presence of a noble metal catalyst such aspalladium or rhodium, including derivatives thereof such as oxides,hydroxides or halides, said catalyst being optionally supported on aconventional carrier such as carbon or diatomaceous earth. Anon-reducible aqueous or non-aqueous inert solvent such as water,ethanol, methanol, ethyl acetate, tetrahydrofuran, diethyl ether ordioxane is used. Hydrogenation may be conducted at atmospheric orelevated pressure and is conveniently run at room temperature for aperiod of from about 1-5 hours depending on the solvent and catalystused. If an equivalent weight of a base such as an alkali metal oralkaline earth metal hydroxide or an amine is employed during thehydrogenation, the product may be recovered in the form of a carboxylicacid salt. Removal of the β-trimethylsilylethyl ester, another usefulprotecting group, is conveniently achieved by treatment with a source offluoride ions. Other ester protecting groups can be similarly removed bymethods well-known to those skilled in the art.

In a second main process (Process II), the reaction sequence is as shownbelow: ##STR42##

As can be seen Process II is substantially the same as Process I (exceptthat Y must be H) up through the thermal cyclization step which producesthe 2-substituted penem. A 6-substituent, however, if desired, is nowincorporated at this stage by reaction of the 2-penem with a suitableelectrophile in an inert solvent (e.g. tetrahydrofuran, diethyl ether,dimethoxyethane, and the like) and in the presence of a strong base. Inthis procedure the 2-penem can be reacted in the form of the free acid(obtained by de-blocking as described above) in the presence of abouttwo equivalents of base or, alternatively, a suitable 2-penem ester maybe used in the presence of about one equivalent of base. Any ester inertto anion chemistry (the reaction involves anion formation with basefollowed by reaction of the electrophile with the penem anion) may beemployed, e.g. (lower)alkyl such as methyl, ethyl, n-propyl or t-butyl,phenyl, trichloroethyl, methoxymethyl, silyl such as trimethylsilyl ort-butyldimethylsilyl, and the like. Penem esters having activatedmethylene groups such as p-nitrobenzyl are not suitable and, if the2-penem ester is of this type, it must be first de-blocked and eitherused as the free acid or converted to a suitable ester. The particularbase used is not critical and the usual strong bases such as sodiumhydride, phenyl lithium or butyl lithium are suitable. Most preferably,however, a lithium disilylamide or a lithium dialkylamide such aslithium dicyclohexylamide (LDCA), lithium diethylamide, lithiumdimethylamide or lithium di-isopropylamide (LDA) is used. Theelectrophile is selected so as to generate the desired Y-substituentupon reaction with the anion and may be, for example, a halogen (e.g.Br₂, I₂), an alkyl halide (e.g. CH₃ I) or a similar halide such as analiphatic, cycloaliphatic, cycloaliphatic-aliphatic, phenyl(lower)alkyl,heterocyclic, heterocyclic-thio, heterocyclic-thio-(lower)alkyl, orheterocyclic-(lower)alkyl, halide, a tosylate or mesylate (e.g.##STR43## φCH₂ CH₂ CH₂ OSO₂ CH₃, etc.), an epoxide ##STR44## anepisulfide ##STR45## an aldehyde (e.g. CH₃ CHO, C₆ H₅ CH₂ CHO), a ketone##STR46## or an ester (e.g. CH₃ CH₂ COOCH₃ or C₆ H₅ COOCH₃).Representative examples of other suitable electrophiles are shown below:##STR47## A most preferred electrophile is acetaldehyde which gives riseto the hydroxyethyl 6-substituent. Introduction of the 6-substituent bythis process is preferably carried out with cooling (e.g. -80° to 0° C.)according to the general procedure described in Canadian Journal ofChemistry, 50(19), 3196-3201 (1972).

After formation of the desired 2,6-penem, any ester protecting group maybe removed as discussed above to give the de-protected product.

The third main reaction process (Process III) can be understood from thefollowing scheme: ##STR48##

The 4-tritylthio-2-azetidinone of Process III is formed as described inProcess II (Variation 3). The ring nitrogen of the azetidinone is thenprotected by a conventional easily removable blocking group such astriorganosilyl (e.g. trimethylsilyl or t-butyldimethylsilyl),methoxymethyl, methoxyethoxymethyl, tetrahydropyranyl, and the like.Introduction of the desired Y-substituent at the 1-position of theazetidinone is then achieved by reaction of an appropriate electrophilewith the N-protected azetidinone in the presence of a strong base(reaction conditions as described above in connection with Process II).At this point the process diverges into two routes depending on the timeof de-blocking the azetidinone.

In one route the N-protected intermediate is de-blocked by conventionalprocedures (e.g. acid hydrolysis)and then converted to the 2,6-penem viaester formation, chlorination of the hydroxy ester, conversion of thechloro ester to a phosphorane, conversion of the phosphorane to a heavymetal mercaptide, acylation of the mercaptide with ##STR49## thermalcyclization of the resulting phosphorane to give the 2,6-penem ester andremoval of the carboxylprotecting group. Reaction conditions for thesesteps are as disclosed in connection with Process II (Variation 3).

An alternative route involves the steps of converting the N-protectedazetidinone to a heavy metal mercaptide, acylating the mercaptide withthe moiety ##STR50## removing the N-protecting group, reacting thede-protected azetidinone with the glyoxylate ester, chlorinating,reacting the chloro ester with the phosphine to give the phosphorane,cyclizing the phosphorane to give the penem ester and removing thecarboxyl-protecting group to give the 2,6-penem. Reaction conditions forthese steps are as disclosed previously.

In preparing the 2-penem or 2,6-penem compounds according to the aboveprocesses, free functional groups in substituents X or Y which do notparticipate in the reaction may be temporarily protected in a mannerwhich is itself known, such as free amino groups by acylation,tritylation or silylation, free hydroxyl groups, for example, byetherification or esterification, mercapto groups by esterification, andfree carboxyl or sulfo groups, for example, by esterification, includingsilylation. After the reaction has taken place, these groups can, ifdesired, be liberated, individually or jointly, in a manner which isitself known.

Additionally, it is possible in compounds of formula I to functionallymodify the 2- and/or 2,6-substituents during or at the conclusion of thereaction procedures according to known processes to obtain othersubstituents included within the scope of the present invention. Thus,for example, carbonyl groups can be reduced to alcohol groups,unsaturated aliphatic groups can be halogenated, amino groups can bealkylated or acylated, nitro groups can be converted to hydroxyamino andamino groups, hydroxyl groups can be etherified or esterified, etc.

The penem free acid compounds may be converted to pharmaceuticallyacceptable salts thereof or to easily removable esters thereof(particularly physiologically cleavable esters). Salts may be formed byreaction of the free acid with a stoichiometric amount of a suitablenon-toxic acid or base in an inert solvent followed by recovery of thedesired salt as by lyophilization or precipitation. Esters (inparticular physiologically cleavable esters) may be prepared in ananalogous manner to preparation of the corresponding esters ofpenicillins and cephalosporins. Resulting mixtures of isomers can beseparated into the individual isomers according to known methods.Mixtures of diastereomeric isomers, for example, can be separated byfractional crystallization, adsorption chromatography (column orthin-layer) or other suitable separation methods. Resulting racematescan be resolved into the antipodes in the customary manner, for exampleby forming a mixture of diastereomeric salts with optically activesalt-forming reagents, separating the diasteromeric salts and convertingthe salts into the free compounds, or by fractional crystallization fromoptically active solvents.

The present invention also comprises those embodiments according towhich compounds used as intermediate products are used as startingmaterials and the remaining process steps are carried out with these, orthe process is discontinued at any stage. Furthermore, startingmaterials can be used in the form of derivatives or can be formed duringthe reaction.

The free acid penem compounds provided by the present invention andpharmaceutically acceptable salts and physiologically cleavable estersof said acids have been found to be potent broad-spectrum antibacterialagents useful in the treatment of infectious diseases in animals,including man, caused by both Gram-negative and Gram-positive organisms.The compounds are also of value as nutritional supplements in animalfeeds and as agents for the treatment of mastitis in cattle.

The 2-penem acids (and physiologically cleavable esters andpharmaceutically acceptable salts thereof) provided according to thepresent invention (i.e. compounds of general formula I wherein Y=H)possess antibacterial activity per se and are also useful intermediates(preferably in their carboxyl-protected form) for preparing the2,6-disubstituted penems I via anion formation and reaction with anelectrophile.

The active compounds provided by the present invention may be formulatedas pharmaceutical compositions comprising, in addition to the activeingredient, a pharmaceutically acceptable carrier or diluent. Thecompounds may be administered both orally and parenterally. Thepharmaceutical preparations may be in solid form such as capsules,tablets or dragees, or in liquid form such as solutions, suspensions oremulsions. In the treatment of bacterial infections in man, the activecompounds of this invention may be administered orally or parenterallyin an amount of from about 5 to 200 mg./kg./day and preferably about 5to 20 mg./kg./day in divided dosage, e.g. three or four times a day.They are administered in dosage units containing, for example, 125, 250or 500 mg. of active ingredient with suitable physiologically acceptablecarriers or diluents.

The present invention also provides a method of combatting bacterialinfections in animals, particularly warm-blooded animals, whichcomprises administering an acid of formula I or a physiologicallycleavable ester thereof or a pharmaceutically acceptable salt thereof,or a pharmaceutical composition thereof, to an infected host in anamount sufficient to combat such infection.

Illustrative examples of the preparation of starting materials andend-products of the present invention follow. All temperatures are indegrees Centigrade. For the sake of convenience, certain abbreviationsare employed in the examples. Definitions of the less obvious of theseabbreviations are as follows:

CSI: chlorosulfonyl isocyanate

pet. ether: petroleum ether

b.p.: boiling point

n.m.r.: nuclear magnetic resonance

h: hour

ether: diethyl ether (unless otherwise indicated)

Celite: Trademark of Johns-Manville Products Corporation fordiatomaceous earth

psi: pounds per square inch

r.t.: room temperature

PNB: p-nitrobenzyl

m.p.: melting point

LAH: lithium aluminum hydride

n-BuLi: n-butyl lithium

MIBK: methyl isobutyl ketone

Et: C₂ H₅ --

Tr: --C(C₆ H₅)₃

Me: CH₃ --

THF: tetrahydrofuran

Ph: phenyl

DMF: dimethylformamide

TEA: triethylamine

PNBG: p-nitrobenzyl glyoxylate

THP: tetrahydropyranyl

TFA: trifluoroacetic acid

HMPT (or HMPA): hexamethylphosphorus triamide

LDA: lithium diisopropyl amide

Ac: CH₃ CO--

Ms: CH₃ SO₂ --

DMAP: 4-dimethylaminopyridine

Preparation of Starting Materials Preparation of4-Tritylthio-2-azetidinone Intermediates 1.1-(Trimethylsilyl)-4-tritylthio-2-azetidinone ##STR51##

A solution of 4-tritylthio-2-azetidinone (345 mg, 1 mmole),1,1,1,3,3,3,-hexamethyldisilazane (80 mg, 0.5 mmole) andchlorotrimethylsilane (55 mg, 0.5 mmole) in dichloromethane (20 ml) washeated under reflux for 18 h. Concentration of the reaction mixture leftvirtually pure title compound. δ(ppm, CDCl₃): 7.32 (15H, m, aromatics),4.22 (1H, dd, H-4), 2.67 (1H, dd, J=4.1, J=16, H-3), 2.22 (1H, J=2.2,J=16, H-3), 0.3 (9H, s, CH₃).

2. 1-(t-Butyldimethylsilyl)-4-tritylthio-2-azetidinone ##STR52##

Triethylamine (1.62 ml, 11.6 mmoles) was added dropwise in 5 min to acooled (0°) and stirred solution of 4-tritylthio-2-azetidinone (3.5 g,10.1 mmoles) and chloro-t-butyldimethylsilane (1.68 g, 12.7 mmoles) inDMF (35 ml). The reaction mixture was stirred at room temperature for 18h, diluted with water (250 ml) and ether (200 ml). The organic phase waswashed with water (3×50 ml), dried and concentrated to leave an oil(4.33 g). Crystallization from pentane gave a total of 4.1 g (89%) ofthe title compound as a white solid, m.p. 113°-4°. δ(ppm, CDCl₃): 7.45(15H, m, aromatics), 4.2 (1H, dd, H-4), 2.63 (1H, dd, J=4, J=16, H-3),2.13 (1H, dd, J=2, J=16, H-3), 1.0 (9H, s t-Bu), 0.35 (6H, s, Me).

ν_(c=o) 1735 cm⁻¹. Anal. calc'd for C₂₈ H₃₃ NOSSi: C, 73.15; H, 7.24; N,3.05; S, 6.97%. Found: C, 73.27; H, 7.32; N, 2.97; S 6.94%.

3. 1-Methoxymethyl-4-tritylthio-2-azetidinone ##STR53##

A solution of 4-tritylthio-2-azetidinone (1.38 g, 4.0 mmoles) in THF (10ml) was added to a well stirred suspension of sodium hydride (200 mg ofcommercial 50%, 4.1 mmoles, washed with pentane) in THF (10 ml)maintained at -15°. Methanol (12 drops) was added and the mixture wasstirred at -15° for 0.5 h. Methoxymethyl bromide (0.58 g, 4.6 mmoles)was added and the mixture was stirred for 2 h, diluted with ether,washed with water and brine, dried and concentrated to leave an oil(1.72 g). Crystallization from pentane gave a white solid (1.41 g) m.p.72-76 δ(ppm, CDCl₃): 7.3 (15H, m, aromatics), 4.4 (3H, m, NCH₂ O andH-4), 3.22 (3H, s CH₃), 2.76 (2H, m, H-3).

4. 1-(Methoxyethoxymethyl)-4-tritylthio-2-azetidinone ##STR54##

To a suspension of tetrabutylammonium bromide (322 mg, 1 mmole) andpotassium hydroxide (85%, 70 mg, 1.1 mmole) in dichloromethane (10 ml)cooled to 5° was added with vigorous stirring 4-tritylthio-2-azetidinone(345 mg, 1 mmole) and methoxyethoxymethyl chloride (187 mg, 1.5 mmole).The mixture was stirred at room temperature for 2 h, the solvent wasevaporated and the residue partitioned between water and ethyl acetate.The dried organic phase was concentrated to leave a viscous oil (415mg). Purification by column chromatography on silica gel eluting withether (5%)-dichloromethane gave the title compound (206 mg, 48%) as anoil. δ(ppm, CDCl₃): 7.30 (15H, m, aromatics), 4.57 (2H, AB quartet,N--CH₂ O), 4.46 (1H, dd, H-4), 3.50 (4H, s, OCH₂ CH₂ O), 3.30 (3H, s,CH₃), 2.75 (2H, m, H-3).

5. 1-(2'-Tetrahydropyranyl)-4-tritylthio-2-azetidinone ##STR55##

n-Butyl lithium (1.6M, 1.6 ml, 2.56 mmoles) was added dropwise to asolution of 4-tritylthio-2-azetidinone (863 mg, 2.5 mmoles) in THFmaintained at -78°. After stirring for 15 min, 2-chlorotetrahydropyran(560 mg, 4.7 mmoles) was added and the reaction mixture was allowed tocome to room temperature in 1.5 h. The reaction solution was dilutedwith ethylacetate, washed with brine, dried and concentrated to leave anoil (635 mg). Column chromatography on silica gel eluting withdichloromethane-ether gave a mixture of the isomeric title compoundscontaminated with a little starting material. δ(ppm, CDCl₃): 7.28 (15H,m, aromatics), 4.4 (H, dd, H-4), 2.9-2.2 (2H, m, H-3), 4.1-3.2 and2.2-0.7 (tetrahydropyranyl).

6. Preparation of4-Tritylthio-1-(p-nitrobenzyl-2'-triphenyl-phosphoranylidene-2'-acetate)-2-azetidinone##STR56## 1-(1'-carboxy-1'-hydroxymethyl)-4-tritylthio-2-azetidinonetriethylamine salt ##STR57##

To a solution of 4-tritylthio-2-azetidinone (3.5 g, 10.15 mmol) intetrahydrofuran (8 ml) was added triethylamine (1.42 ml, 10.15 mmol) andglyoxylic acid hydrate (1.02 g, 10.15 mmol). The mixture was stirred atroom temperature with 4 Å mol. sieves* (volume of 8 ml) for 1 h andallowed to stand at room temperature overnight. The solidified mixturewas diluted with methylene chloride and filtered; the filtrate wasevaporated and the residue crystallized from pentane to give 5.18 g(98%) of title compound as a white solid mp 112°-5° C.; ir ν_(max) :3100-3600, and 1755 cm⁻¹ ; ¹ Hmr (CDCl₃) δ: 7.3 (15H, m), 4.92 and 5.10(1H, 2s), 4.50 (1H, dd, J=8 Hz, J=3 Hz), 3.0 (1H, dd, J=15 Hz, J =7Hz),3.1 (6H, q, J=7 Hz), 2.70 (1H, dd, J=15 Hz, J=3 Hz), 2.0-3.5 (2H, m) and1.21 ppm (9H, t, J=7 Hz).

1-(1'-carboxy-1'-chloromethyl)-4-tritylthio-2-azetidinone ##STR58##

A cooled (ice bath) solution of the triethylamine salt of1-(1'-carboxy-1'-hydroxymethyl)-4-tritylthio-2-azetidinone (1.04 g, 2.0mmol) in methylene chloride (5 ml) was treated dropwise, under N₂, withthionyl chloride (0.16 ml, 2.2 mmol) in methylene chloride (2 ml). Thesolution was stirred at room temperature for 20 min and concentrated.The residue was diluted with benzene and filtered over a Celite/charcoalbed. The filtrate was evaporated in vacuo to give 870 mg (quantitative)of the title compound as an amorphous solid. It was used in the nextstep without further purification. ir ν_(max) : 1775 cm⁻¹ ; ¹ Hmr(CDCl₃) δ: 9.22 (1H, bs), 7.27 (15H, m), 5.3 and 5.2 (1H, 2d, J=2 Hz),4.6 (1H, m) and 2.8 ppm (2H, m).

1-(1'-carbo-p-nitrobenzyloxy-1'-chloromethyl)-4-tritylthio-2-azetidinone ##STR59##

To a cooled (ice bath) solution of DMF (0.17 ml, 2.2 mmol) in*chloroform (4.4 ml) was added dropwise oxalyl chloride (0.19 ml, 2.2mmol). The mixture was stirred 5 min in ice, then 20 min at roomtemperature. The solution was cooled in an ice bath and treated dropwisewith 1-(1'-carboxy-1'-chromethyl)-4-tritylthio-2-azetidinone (854 mg, 2mmol) in chloroform (2 ml) followed by a 1M solution of pyridine intetrahydrofuran (2.2 ml, 2.2 mmol); the solution was stirred at roomtemperature for 30 min, cooled to 0° C. and treated dropwise withparanitrobenzyl alcohol (370 mg, 2.2 mmol) in tetrahydrofuran/chloroform(1:1, 2 ml) and triethylamine (0.31 ml, 2.2 mmol). The solution wasstirred at room temperature for 30 min, then evaporated. The residue wasdiluted with benzene and filtered over a Celite/charcoal bed and thefiltrate was evaporated in vacuo. The crude chloro ester was purified ona silica gel pad (5 g) and eluted with methylene chloride to give 790 mg(70%) of the title compound as a beige powder. Trituration in ether gavea white solid, mp 168°-9° C. ir ν_(max) : 1780, 1760 cm⁻¹ ; ¹ Hmr(CDCl₃) δ: 8.15 (2H, d, J=9 Hz), 7.49 (2H, d, J=9 Hz), 7.3 (15H, m),5.75 and 5.35 (1H, 2s), 5.3 (2H, s), 4.55 (1H, m), 2.8 (2H, m). Thiscompound was identical to an authentic sample prepared by reaction of4-tritylthio-2-azetidinone with p-nitrobenzyl glyoxylate followed by athionyl chloride treatment.

EXAMPLE 11-(p-Nitrobenzyloxycarbonylmethyltriphenylphosphoranyl)-4-(silvermercaptidyl)-2-azetidinone ##STR60##

A methanol (90 cc) suspension of triphenylmethyl mercaptan (13.8 g, 0.05mmole) was degassed for 0.5 hour with a nitrogen stream. The mixture wascooled down at 0° and sodium hydride (2.4 g, 0.05 mole, 50% oildispersion) was added portionwise. The resulting solution was stirredfor 5 min and 4-acetoxyazetidinone (7.7 g, 0.059 mole) in water (55 cc)was added rapidly. Precipitation of 4-triphenylmethylmercaptoazetidinone (2) occurred immediately. The mixture was stirredfor 4 h at room temperature. The solid was filtered off, washed withwater and dissolved in methylene chloride. The methylene chloridesolution was washed with diluted HCl, water, aqueous sodium bicarbonatewater and brine and dried over MgSO₄ (89.8%, m.p.: 146.5°-147.5° C.)

Anal. Calc'd for C₂₂ H₁₉ NOS: C, 76.49; H, 5.54; N, 4.05; S, 9.28 Found:C, 7.54; H, 5.60; N, 4.00; S, 9.36.

δ(ppm, CDCl₃) 7.60-7.10 (15H, m, H-trityl), 4.62 (1H, bs, NH), 4.40 (1H,dd, J₄₋₃ trans 32 3.0, J₄₋₃ cis =5, H-4), 3.24 (1H, ddd, J_(gem) =15,J₃₋₄ cis =5, J_(3-NH) =1.8, H-3), 2.81 (1H, ddd, J_(gem) =15, J₃₋₄ trans=3.0, J_(3-NH) =1.2, H-3).

ν_(c=o) (CHCl₃) 1760, ν_(NH) 3340. ##STR61##

Hydrated p-nitrobenzyl gloxylate (4.54 g, 0.02 mole) and azetidinone 2(6.90, 0.02 mole) were refluxed in benzene through a Dean Starkcondenser filled with 3 Å molecular sieves for 24 h. Further glyoxylate(2×454 mg, 2 mmoles) was added with reflux period (18 h) after eachaddition. The mixture was diluted with ether, washed with 5% aqueousHCl, water, aqueous 5% NaHCO₃ water and brine. It was dried over MgSO₄(12 g, quantitative) A small fraction of the epimeric mixture wasseparated on a silica gel plate (CH₂ Cl₂ -ether 6:4)

Isomer A:

Rf=0.87, m.p.=170.5°-171.5°

δ(ppm, CDCl₃) 8.07 (2H, d, J=9, Hm aromatic), 7.45 (part of d, Hoaromatic), 7.40-7.00 (15H, m Trityl), 5.25 (2H, s, CH₂ -PNB), 4.75 (1H,s, H--C--O) 4.37 (1H, dd, J₃₋₄ trans =3, J₃₋₄ cis =4, H-3), 2.83 (1H,dd, J_(gem) =16, J₄₋₃ cis =4, H-4), 2.10 (1H, dd, J_(gem) =16, J₄₋₃trans =3, H-4), 1.42 (b.s., OH).

ν_(c=o) (CHCl₃) 1770, 1760 (shoulder), ν_(NO).sbsb.2 1525, ν_(OH) 3475.

Isomer B:

Rf=0.75, m.p.=152°-153°.

δ(ppm, CDCl₃), 8.13 (2H, d, J=9, Hm aromatic), 7.47 (2H, d, J=9, Hoaromatic), 7.40-7.00 (15H, m, trityl), 5.30 (3H, s, CH₂ -PNB, H--C--O),4.45 (1H, t, J=3.5, H-4), 2.90-2.70 (2H, AB part of ABX, H-4), 1.55(b.s., OH).

ν_(c=o) (CHCl₃) 1767, 1755 (shoulder), ν_(NO).sbsb.2 1525, ν_(OH) 3500.##STR62##

A cold (-15°) THF (150 cc, dried over molecular sieves) solution ofazetidinone 3 (12 g, 21.7 mmoles) was treated with pyridine (1.9 g, 24.1mmoles, 1.94 cc) and dropwise with thionyl chloride (2.86 g, 24 mmoles,1.88 cc) under a nitrogen atmosphere. The mixture was stirred for 45 minat -15°. The precipitate was filtered off and washed with benzene.Evaporation of solvent gave a residue which was taken up in benzene andtreated with activated charcoal (11.7 g, 94%, crystallized out fromchloroform).

δ(ppm, CDCl₃) 8.17 (2H, d, J=8, Hm aromatic), 7.67-7.00 (17H, m, Hoaromatic, Tr-H), 5.80 (s, H--C--Cl), 5.37, 5.33 (2s, H--C--Cl, CH₂-PNB), 4.81 (1H, m, H-4) 3.27-2.40 (2H, m, H-3).

ν_(c=o) (KBr film) 1785, 1770 ν_(NO).sbsb.2 1525. ##STR63##

A THF (100 cc, distilled over LAH) solution of chloroazetidinone 4 (11.6g, 20.2 mmoles) was treated with triphenyl phosphine (7.86 g, 30.0mmoles) and 2,6-lutidine (2.36 g, 2.56 cc, 22.0 mmoles). The mixture wasrefluxed for 72 h. The precipitate was filtered off and washed withether. The organic solution was washed with 2% aqueous HCl and 5%aqueous bicarbonate and dried over MgSO₄. Evaporation of solvent gave aresidue which was purified through silica gel pad (200 g). The desiredphosphorane was eluted with 30,40 and 50% ether-benzene (11.4 g, 70.4%,m.p.: 201°-202°).

Anal. Calc'd for C₄₉ H₄₀ N₂ O₅ SP: C, 73.57; H, 5.04; N, 3.50; S, 4.01.Found: C, 73.58; H, 4.91; N, 3.44; S, 3.87.

ν_(c=o) (CHCl₃) 1740, ν phosphorane (1620, 1610), ν_(NO).sbsb.2 1525.##STR64##

4-Tritylmercapto azetidinone 5 (1.6 g, 2 mmoles) was dissolved in CH₂Cl₂ (20 cc) and the solvent was flushed down at 55°-60°. Phosphorane 5at 55°-60° was dissolved in preheated (55°-60°) methanol (32 cc).Immediately after the obtention of a methanolic solution of 6 it wastreated with a preheated (55°-60°) mixture of methanolic 0.15M silvernitrate solution (16 cc, 1.2 eq) and pyridine (174 mg, 178μl, 2.2mmoles, 1.1 eq). The warming bath was then immediately removed. Themixture was stirred at room temperature for 2 h and at 0° C. for 1 h.The silver mercaptide 6 was filtered off, washed twice with cold (0°)methanol and three times with ether. (1.12 g, 84.5%, m.p.: 130-135dec.).

ν_(c=o) (CHCl₃) 1795, 1725 (shoulder), νphosphorane (1620, 1605),ν_(NO).sbsb.2 1530.

EXAMPLE 21-(p-Nitrobenzyloxycarbonylmethyltriphenylphosphoranyl)-4-(silvermercaptidyl)-2-azetidinone ##STR65##

A solution of phosphorane 7 (1.796 g. 3.0 mmoles) in chloroform (3 ml)was diluted with methanol (90 ml), cooled at 0° C. under nitrogenatmosphere and treated successively with silver nitrate (0.51 g, 3.0mmoles) and potassium carbonate (0.33 g, 2.4 mmoles). The reactionmixture (protected from light) was stirred at 0° C. for 15 min., thenthe cooling bath was removed and stirring was continued for 3 h. Thereaction mixture was cooled down to -10° C., stirred for 1 h andfiltered; the silver mercaptide was successively washed with coldmethanol and ether; 1.91 g, M.P.: 138°-145° C. dec, 96%. I.R. (nujol)cm⁻¹ : 1748, 1620 and 1605. An analytical sample was obtained bypreparative TLC (ethyl acetate); M.P.: 140°-5° C. dec, calc'd for C₃₀H₂₄ N₂ O₅ SPAg: C, 54.31; H, 3.65; N, 4.22; S, 4.83. Found: C, 54.11; H,3.48; N, 3.92; S, 4.62.

EXAMPLE 31-(p-Nitrobenzyloxycarbonylmethyltriphenylphosphoranyl)-4-(silvermercaptidyl)-2-azetidinone A. Use of aniline as base ##STR66##

A solution of phosphorane 7 (1.8 g, 3.0 mmoles) in chloroform (4 ml) wasdiluted with methanol (90 ml), cooled to -15° C. under nitrogenatmosphere and treated successively with silver nitrate (0.56 g, 3.3mmoles) and aniline (1.5 ml, 16.5 mmoles). The reaction mixture(protected from light) was stirred at -15° C. for 0.5 h and then thecooling bath was removed and stirring was continued for 24 h. Thereaction mixture was cooled to -10° C. and stirred for 1 h before beingfiltered; the silver mercaptide was successively washed with coldmethanol and ether; 1.55 g, M.P. 114°-5° C. dec. 77.9%. IR (nujol)cm⁻¹ ;identical to compound of Example 2.

Silver-1-(paranitrobenzyl2'-triphenylphosphoranylidene-2'-acetate)-2-azetidinone-4-thiolate B.Use of 4-dimethylaminopyridine (DMAP) as base ##STR67##

A solution of the above S-acetyl phosphorane (17.96 g, 30 mmol) inmethanol and dichloromethane (1:2, 450 ml) was purged with nitrogen(5-10 min), cooled to 5° C. and treated successively with silver nitrate(5.35 g, 31.5 mmol) and 4-dimethylaminopyridine (3.85 g, 31.5 mmol). Theice-bath was removed and the solution refluxed vigorously for 2 h andthen stirred at room temperature for 1 h. The colored reaction mixturewas treated with charcoal, filtered and evaporated. The residue wasredissolved in the minimum amount of dichloromethane and added dropwise,with stirring to cold methanol (300 ml). The precipitated silver saltwas collected by filtration, washed with ether and dried; 18.1 g (91%);ir (CHCl₃) ν_(max) : 1745 (C═O of β-lactam) and 1607 cm⁻¹ (C═O ofester).

Silver-1-(paranitrobenzyl2'-triphenylphosphoranylidene-2"-acetate)-2-azetidinone-4-thiolate C.Use of diazabicycloundecene (DBU) as base ##STR68##

The above S-acetylphosphorane (36.0 g, 0.060 mol) was dissolved inmethylene chloride 120 ml. The solvent was evaporated in order to obtainan oil. The resulting oily residue was dissolved in warm (35° C.)methanol (240 ml) and treated rapidly with a methanolic (420 ml)solution of silver nitrate (10.68 g, 0.0628 mol). The resulting solution(or suspension) was stirred at room temperature for 5 min, cooled down(ice bath) and a DBU (8.96 ml, 0.060 mol) solution in methanol (20 ml)was added over a 5 min period. The mixture was stirred for 5 min. Thesolid was filtered, washed once with cold (0° C.) methanol and ether anddried under vacuum; 37.0 g (93%); ir (nujol mull) ν_(max) 1745 (c═O) and1600 cm⁻¹ (phosphorane).

D. Use of pyrrolidine as base Silver 1-(paranitrobenzyl2'-triphenylphosphoranylidene-2"-acetate)-2-azetidinone-4-thiolate##STR69##

To a cold (0° C.) solution of 4-acetylthio-1-(paranitrobenzyl2"-triphenylphosphoranylidene-2"-acetate)-2-azetidinone (0.60 g, 1.0mmol) in CH₂ Cl₂ (2 ml) was added MeOH (4 ml), a solution of AgNO₃ inMeOH (0.14N, 7.86 ml, 1.1 mmol) and a solution of pyrrolidine (0.92 ml,1.1 mmol) in MeOH (2 ml). The cooling bath was removed and the reactionmixture was stirred for 1.75 h, cooled to -10° C., stirred for 0.25 hand filtered. The solid was washed with cold MeOH and dried in vacuo;0.548 g, m.p. 115° C., 82.4%. ir (nujol) ν_(max) : 1755 (C═O) and 1600cm⁻¹ (aromatics).

EXAMPLE 4 Mercuric(II)-[2'-Triphenylphosphoranylidene-2'-acetate]-2-azetidinone-4-thiolate##STR70##

A solution of I (2.4 g, 3 mmoles) in dichloromethane (15 ml) was cooledto 5° C. and treated with a solution of mercuric acetate (0.525 g, 1.65mmole) dissolved in methanol (15 ml). After stirring at 5° C. for 2 h,the solvent was evaporated and the residue redissolved indichloromethane and washed with cold water. The organic solution afterbeing dried (MgSO₄) and treated with charcoal, was evaporated to give afoam which crystallized when triturated in ether. Yield: 1.73 g (91%)M.P. 123°-127° C., I.R. (CHCl₃) 1745 cm⁻¹ (ν_(c=o) β-lactam) 1608 cm⁻¹(phenyl)

EXAMPLE 5 A. Preparation of3-(1'-Hydroxy-1'-ethyl)-1-methoxymethyl-4-tritylthio-2-azetidinones##STR71## (a) (1'S,3S,4R and 1'R,3R,4S)isomer (isomer C)

A solution of lithium diisopropyl amide was prepared in THF (5 ml) at-78° C. from n-butyl lithium (1.6M, 1.0 ml, 1.6 mmol) anddiisopropylamine (0.25 ml, 1.84 mmol). After 30 min a solution of1-methoxymethyl-4-tritylthio-2-azetidinone (491 mg, 1.42 mmol) in THF (6ml) was added dropwise and the solution was stirred for 15 min.Acetaldehyde (3.0 ml) was added dropwise, followed, after 20 min, bywater (30 ml). The mixture was acidified to pH 3 with 2% HCl andextracted with ethyl acetate (5×20 ml). The combined organic phases werewashed with brine, dried and concentrated to leave an oil whichcrystallized upon trituration with ether: 440 mg, 80%, mp 188.5°-9° C.;¹ Hmr (CDCl₃) δ: 7.3- (15H, m, aromatics), 4.37 (2H, ABq, N--CH₂ O),4.32 (1H, d, J=2, H-4), 3.17 (3H, s, OCH₃), 3.32-2.70 (2H, m, H-3 andH-5), and 1.12 ppm (3H, d, J=7, CH₃); Anal. calcd for C₂₆ H₂₇ NO₃ S: C72.02, H 6.28, N 3.23, S 7.39; found: C 71.99, H6.02, N 3.21, S 7.40%.

(b) (1'S,3S,4R and 1'R,3R,4S) and (1'R,3S,4R and 1'S,3R,4S) (isomers Cand B)

A solution of lithium diisopropyl amide (0.482 mmol) is prepared at -78°C. in dry ether (3 ml) from butyl lithium 0.191 ml of 2.52M solution inhexane, 0.482 mmol) and diisopropyl amine (0.067 ml, 0.482 mmol). After20 min, a solution of (4R and 4S)1-methoxymethyl-4-tritylthio-2-azetidinone (0.171 g, 0.439 mmol) in amixture of dry ether (1 ml) and dry THF (1 ml) was added dropwise andthe resulting clear solution was stirred at -78° C. for 15 min. Asolution of tetrabutyl ammonium fluoride (0.96 ml of a 0.5M solution inTHF, 0.48 mmol) was then added. A precipitate was formed with thegeneration of a slight pink colour. After 5 min at -78° C., the reactionmixture was quenched with freshly distilled acetaldehyde (0.2 ml,excess), and the stirring continued for 15 more min. The work-up wasdone by adding to a saturated solution of ammonium chloride andextracting with ethyl acetate (2×25 ml). The combined organic phaseswere washed with brine and dried over anhydrous magnesium sulfate.Evaporation of the solvent under vacuum gave an oil (0.228 g) which waschromatographed on 10 g of silica gel A mixture of benzene and ethylacetate (6:4) gave 0.106 g (62% recovery) of substrate and a mixture ofthe two isomer alcohols which were separated by chromatography on thicklayer plates (same solvent-system). The alcohol with the high Rf (0.033g, 17%) was identical to the above isomer (isomer C): mp 188.5°-189° C.(Ether-dichloromethane); The alcohol with low Rf (0.030 g, 16%) (isomerB), was obtained as an oil which crystallized with difficulty fromhexanes: mp 94°-95° C. ir (CH₂ Cl₂) ν_(max) : 3600 (OH), 1760 cm⁻¹(C═O); ¹ Hmr (CDCl₃) δ:6.9-7.5 (15H, m, aromatics), 4.2 (2H, center ofABq, J=11.5, CH₂ --O--CH₃), 4.28 (1H, d, J=2.0, 4-H), 3.65 (1H, centerof a broad sextet, H-1'), 3.3 (1H, dd, J₃,4 trans =2.5, J₃,1' =5.5, H₃),3.15 (3H, s, O--CH₃), 1.55 (1H, broad s, OH-1'), 1.05 (3H, d, J=6.5,H-2'); Anal. calcd for C₂₆ H₂₇ NO₃ S: C 72.02, H 6.28, N 3.23, S 7.39;found: C 71.77, H 6.36, N 3.15, S 7.43%.

B. Preparation of trans3-Acetyl-1-methoxymethyl-4-tritylthio-2-azetidinone ##STR72##

Lithium diisopropylamide was prepared under a nitrogen atmosphere at-78° C. in the usual manner from diisopropylamine (0.34 ml, 2.4 mmol)and n-butyl lithium (1.1 ml of a 2.2M solution in hexane, 2.4 mmol) inTHF (3 ml). A solution of 1-methoxymethyl-4-tritylthio-2-azetidinone(0.78 g, 2 mmol) in THF (3 ml) was added dropwise and, after stirring at-78° C. for 20 min, ethylacetate (0.53 g, 6 mmol) was added in oneportion and stirring continued for 0.75 h at -78° C. The reactionmixture was diluted with ether and washed with an ammonium chloridesolution, water and brine, dried and concentrated to give an oil (0.7g). Purification was achieved by chromatography over silica gel (20 g)eluting with increasing amounts of ether in benzene. The pertinentfractions were concentrated to give the title material as a colorlessoil (0.32 g, 37%); ¹ Hmr (CDCl.sub. 3) δ: 7.7-6.8 (15H, aromatics), 4.85(1H, d, J=2, H-4), 4.5 (2H, s, N--CH₂ --O), 3.9 (1H, d, J=2, H-3), 3.22(3H, s, CH₃) and 2.0 ppm (3H, s, CH₃); ir ν_(max) : 1770, 1710 cm⁻¹.

C. Preparation of trans3-Acetyl-1-(t-butyldimethylsilyl)-4-tritylthio-2-azetidinone ##STR73##

Diisopropyl lithium amide was prepared in the usual manner fromdiisopropylamine (0.18 ml, 1.24 mmol) and n-butyllithium (0.78 ml of a1.6M solution in hexane, 1.24 mmol) in THF (8 ml). A solution of1-(t-butyldimethylsilyl)-4-tritylthio-2-azetidinone (0.46 g, 1 mmol) inTHF (8 ml) was added dropwise at -78° C. After a 5 min stirring period,ethyl acetate (1 ml) was added in one portion and the mixture wasstirred 3 h at -78° C. The mixture was acidified with cold hydrochloricacid (0.5N) to pH 6 and extracted with ethyl acetate (2×20 ml). Thecombined organic phases were dried and concentrated to give an oil (0.5g) which crystallized from pentane: 200 mg total, 40%, mp 122°-4° C.; irν_(max) : 1750, 1710 cm⁻¹ ; ¹ Hmr (CDCl₃) δ: 8-7.1 (15H, m, aromatics),4.83 (1H, d, J=2, H-4), 3.38 (1H, d, J=2, H=3), 1.80 (3H, s, CH₃), 0.92(9H, s, Bu and 0.3 ppm (6H, s, CH₃).

D. Preparation oftrans-1-(t-Butyldimethylsilyl)-3-formyl-4-tritylthio-2-azetidinone##STR74##

To a cooled (-78° C.) solution of diisopropylamine (0.34 ml, 2.4 mmol)in tetrahydrofuran (5 ml) was added dropwise, under N₂, a solution of1.5M n-BuLi (1.6 ml, 2.4 mmol). After stirring for 30 min, a solution of1-(t-butyldimethylsilyl)-4-tritylthio-2-azetidinone (1.0 g, 2.18 mmol)in tetrahydrofuran (5 ml) was added dropwise and stirring was maintainedfor 30 min. Ethyl formate (0.8 ml, 9.9 mmol) was added and the cooledsolution was stirred for 10 min. The reaction mixture was washedsuccessively with cold 1N hydrochloric acid (5 ml), 1M sodiumbicarbonate (6 ml), water (10 ml) and brine. The organic layer was dried(MgSO₄), evaporated and crystallized from pentane to give 810 mg (76%)of formate as a white solid mp 132°-3° C.; ir (CHCl₃) ν_(max) : 1760,1715 cm⁻¹ ; ¹ Hmr (CDCl₃) δ: 9.0 (1H, d, J=1.25 Hz), 7.30 (15H, m), 4.7(1H, d, J =1.5 Hz) and 3.5 ppm (1H, t, J=1.5 Hz).

Note:

(a) diisopropyl amine was distilled over CaH and stored on KOH

(b) tetrahydrofuran was distilled over L.A.H. and stored on molecularsieves 3 Å

(c) ethyl formate was stirred at room temperature with K₂ CO₃, thendistilled over P₂ O₅

(d) n-BuLi was titrated with 1N hydrochloric acid

E. Preparation of1-(t-Butyldimethylsilyl)-3-(1'-hydroxy-1'-ethyl)-4-tritylthio-2-azetidinones.(4 isomers) ##STR75##

n-Butyllithium (1.6M, 3.4 ml, 5.44 mmol) was added in 5 min to asolution of diisopropylamine (0.847 ml, 6.23 mmol) in THF (30 ml)maintained at -78° C. After 0.5 h a solution of1-(t-butyldimethylsilyl)4-tritylthio-2-azetidinone (2.0 g, 4.4 mmol) inTHF (20 ml) was added; after 15 min acetaldehyde (10 ml) was added inone portion; after another 15 min water (100 ml) was added. The mixturewas acidified (pH 5-6) with dilute hydrochloric acid and extracted withethyl acetate (3×30 ml). The organic phases were washed with brine,dried and concentrated to leave an oil which was found to consist of amixture of four isomers by tlc (labelled isomers A,B,C,D by decreasingorder of polarity).

Crystallization of the oily residue in ethyl acetate-pentane gaveisomers B and C as a white solid and left A and D in the mother-liquors.The four pure compounds were obtained by preparative chromatography(Waters, 500) of the above solid and mother-liquors. The relativeproportions were: A, 17%; B, 32%; C, 39%; D, 12%. In the above reaction,when ether was substituted for THF and the reaction quenched after 1 minat -78° C., the relative proportions of A,B,C, and D were: 12.9, 30.5,38.2 and 18.4%. In ether, when the reaction was allowed to come to 20°C. in 2 h before quenching, the proportions were: 13.4, 24.6, 44, and18%. When one molar equivalent of anhydrous magnesium bromide was addedto the reaction mixture, the proportions changed to: 19.2, 19.7, 30.1and 31%.

Isomer A

This isomer possesses a cis-stereochemistry at C₃ -C₄. It is a racemicmixture composed of the (1'S, 3R, 4R) and the (1'R, 3S, 4S) enantiomers.Compounds later derived from compound A are referred to as "Isomer A".They consist of an enantiomeric mixture and possess the sameconfiguration at C_(1'), C₃ and C₄. Compounds derived from compound A,through a reaction that proceeds with inversion of configuration, willbe referred to as "Isomer D" if the inversion takes place at C₁, and as"isomer C" for the inversion, at C₃ mp 152°-3° C.; ¹ Hmr (CDCl₃) δ:8.0-6.8 (15H, m, aromatics), 4.30 (1H, d, J=5.5, H-4), 3.78 (1H, m,H-1'), 3.10 (1H, dd, J=5.5, J=10, H-3), 1.22 (3H, d, J=6.5, CH₃), 0.95(9H, s, Bu), 0.27 (6H, 2s, CH₃). Anal. calcd for: C₃₀ H₃₇ NO₂ Si: C71.52, H 7.40, N 2.78, S 6.36%. found: C 71.28, H 7.41, N 2.48, S 6.19%.

Isomer B

This isomer possesses a trans-stereochemistry at C₃ -C₄. It is a racemicmixture composed of the (1'R,3S,4R) and the (1'S,3R,4S) enantiomers.Compounds with the same configuration at C_(1'), C₃ and C₄ are referredto as "Isomer B"; ir (CHCl₃) ν_(max) : 1745 cm⁻¹ (C═O); mp 158°-9° C.; ¹Hmr (CDCl₃) δ: 7.60-7.10 (15H, m, aromatics), 4.02 (1H, d, J=0.8 H-4),3.32 (1H, dd, J=3.0, J=0.8, H-3), 3.55-3.15 (1H, m, H-1'), 0.88 (12H,CH₃, and t-Bu), 0.16 (6H, s, CH₃);

Isomer C

This isomer possesses a trans-stereochemistry at C₃ -C₄. It is aracemate formed of the (1'S,3S,4R) and the (1'R,3R,4S) enantiomers.Compounds with the same configuration at C_(1'), C₃ and C₄ are referredto as "Isomer C". mp 134°-6° C.; ¹ Hmr (CDCl₃) δ: 7.60-7.10 (15H, m,aromatics), 4.32 (1H, d, J=1.8, H-4), 3.02 (1H, dd, J=2.7, J=1.8, H-3),3.0-2.5 (1H, dq, J=2.7, J=6, H-1'), 1.02 (3H, d, J=6, CH₃), 0.95 (9H, s,t-Bu), 0.27 (6H, s, CH₃); ir (CHCl₃) ν_(max) : 1735 cm⁻¹ (C═O).

Isomer D

This isomer possesses a cis-stereochemistry at C₃ -C₄. It is a racematecomposed of the (1'R,3R,4R) and the (1'S,3S,4S) enantiomers. Compoundswith the same configuration at C_(1'), C₃ and C₄ are referred to as"Isomer D". mp 171°-2° C.; Hmr (CDCl₃): 7.80-6.90 (15H, m, aromatics),4.70 (1H, d, J=4.5, H-4), 3.02 (1H, dd, J=4.5, J=0.5, H-3), 2.39 (1H,dq, J=0.5, J=6.5, H-1'), 1.0 (3H, d, J=6.5, CH₃), 0.97 (9H, s, t-Bu),0.32 (6H, s, CH₃). Anal. calcd for C₃₀ H₃₇ NO₂ SSi: C 71.52, H 7.40, N2.78, S 6.36%. found: C 71.27, H 7.43, N 2.51, S 6.31%. ##STR76##

A solution of trans3-acetyl-1-(t-butyldimethylsilyl)-4-tritylthio-2-azetidinone (1.0 g, 2mmol) in THF (30 ml) was added dropwise, under a nitrogen atmosphere, toa cooled (0°) and stirred suspension of sodium borohydride (0.38 g, 10mmol) in THF (120 ml). The ice bath was removed and the mixture wasstirred at room temperature for 4 h. It was poured into ice-coldhydrochloric acid (1N, pH 6), stirred for 15 min and extracted withether (3X). The combined ether extracts were dried and concentrated togive an oil (1.04 g) which was crystallized in pentane to give the titlecompounds as a 70:30 mixture of the C and B isomers. mp 119°-121° C.;84%. ##STR77##

A suspension of cuprous iodide (4.78 g, 15 mmol) in ether (50 ml) wascooled to 0° C. and treated under N₂, with a 1.9M solution of methyllithium (26 ml, 50 mmol). The brown solution was stirred at 0° C. for 10min and then cooled to -60° C. and treated dropwise with the trans1-1(t-butyl dimethylsilyl)-3-formyl-4-tritylthio-2-azetidinone (2.43 g,5.0 mmol) in a mixture of tetrahydrofuran (10 ml)/ether (40 ml).Stirring was continued for 3 h. The solution was warmed up to -40° C.and treated carefully with a 1M solution of ammonium chloride. Themixture was filtered over Celite and the organic phase was washed with a1M solution of ammonium chloride (3×5 ml) and then brine and dried oversodium sulfate. Filtration and evaporation gave alcohol, isomer B, whichcrystallized from warm pentane to yield 1.6 g (65%), mp 160°-1° C.; ir(CHCl₃) ν_(max) : 1730 cm⁻¹ ; ¹ Hmr (CDCl₃) δ: 7.32 (15H, m), 4.05 (1H,s), 3.4 (1H, d, J=3 HZ, 3.25-3.55 (1H, m), 1.6 (1H, s), 0.9 (12H, s) and0.1 ppm (6H, s).

NOTE:

(a) tetrahydrofuran and ether were distilled over L.A.H.

(b) methyl lithium was titrated with 1N hydrochloric acid

(c) copper (I) iodide was purified by continuous extraction withanhydrous tetrahydrofuran in a Soxhlet extractor for 18 h, then driedunder vacuum in a dessicator (P₂ O₅) for 18 h. ##STR78##

Methylmagnesium iodide (0.1 ml, 0.1 mmol) was added dropwise to a cooled(0° C.) and stirred solution of trans1-(t-butyldimethylsilyl)-3-formyl-4-tritylthio-2-azetidinone (25 mg,0.05 mmol) in THF (2 ml). The solution was stirred 1.5 h at 0° C.,poured onto an ammonium chloride solution, acidified with a hydrochloricacid solution (1N) and extracted with ether. Drying and concentration ofthe organic extracts left an oil consisting of starting material and asmall amount of a mixture of the two trans title compounds with isomer Bpredominating.

F. Preparation of (1'S,3S,4R and 1'R,3R,4S)1-(t-Butyldimethylsilyl)-3-(1'-trimethylsilyloxy-1'-ethyl)-4-tritylthio-2-azetidinone(isomer C) ##STR79##

A solution of (1'S,3S,4R and 1'R,3R,4S)1-(t-butyldimethylsilyl)-3-(1'-hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone(15 mg, 0.3 mmol) and azidotrimethylsilane (35 mg, 0.30 mmol) in dry THF(6 ml) was stirred at room temperature until disappearance of thestarting material (15 min). Purification of the reaction mixture bycolumn chromatography (silica gel, CH₂ Cl₂) gave the desired compound asa white solid (128 mg, 74%) mp 144°-46° C. ¹ Hmr (CDCl₃) δ: 7.10-7.60(15H, m, aromatics), 4.30 (1H, d, J=1.5, H-4), 2.25-2.89 (2H, m, H-3,H-1'), 0.82-1.07 (12H, m, t-Bu, H-2'), 0.27 (6H, s, CH₃), -0.10 (9H, s,--O--Si(CH₃)₃ ; ir (CHCl.sub. 3) ν_(max) : 1736 cm⁻¹ (C═O).

G. Preparation of (1'S,3R,4R and 1'R,3S,4S)1'(t-Butyldimethylsilyl)-3-(1'-methoxymethoxyether-1'-ethyl)-4-tritylthio-2-azetidinone (isomer A) ##STR80##

n-Butyllithium (ca 12.5 ml of 1.6M solution in hexane, 20 mmol; justenough to obtain a permanent pink coloration) was added dropwise to asolution of (1'S,3R,4R and 1'R,3S,4S)1-(t-Butyldimethylsilyl)-3-(1'-hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone(isomer A) (10.1 g, 20 mmol) in THF (100 ml) maintained at -78°. After a15 min stirring period a solution of bromomethoxymethyl ether (2 ml, 24mmol) in THF (30 ml) was added dropwise. The mixture was stirred 1 h at-78° and 2 h at room temperature and poured into an ammonium chloridesolution (200 ml). Extraction with ethyl acetate (3×200 ml), washingwith brine, drying with sodium sulfate and concentration gave the crudetitle compound which was purified by chromatography on silica geleluting with increasing amounts of ether in benzene (10.4 g 95%). ¹ Hmr(CDCl₃) δ: 7.1-7.5 (15H, m, aromatics), 4.47 (1H, d, H-4), 4.23 (2H,ABq, J=7, O--CH₂ --O), 3.1-3.4 (2H, m, H-3 et H-1'), 3.23 (3H, s,O--CH₃), 1.37 (3H, d, J=6.5, CH₃), 0.97 (9H, s, Bu) and 0.25 ppm (6H,2s, CH₃).

H. Preparation of (1'S,3S,4R and 1'R,3R,4S)1-(t-Butyldimethylsilyl)-3-(1'-formyloxy-1'-ethyl)-4-tritylthio-2-azetidinone(isomer C) ##STR81##

A solution of (1'S,3S,4R and 1'R,3R,4S)1-(t-butyldimethylsilyl)-3-(1'-hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone(isomer c) (50 mg, 0.1 mmol), p-bromobenzenesulfonylchloride (100 mg,0.4 mmol) and dimethylaminopyridine (24 mg, 0.2 mmol) in DMF (3 ml) wasstirred at room temperature until disappearance of starting material(0.5 h). Then the reaction mixture was diluted with water and extractedwith ether. The organic extracts were washed with brine, dried (MgSO₄)and evaporated. The title compound was purified by columnchromatography. ¹ Hmr (CDCl₃) δ: 7.80 (1H, s, CHO), 7.20-7.66 (15H, m,aromatics), 3.90-4.36 (1H, m, H-1'), 4.07 (1H, d, J=2, H-4), 3.22 (1H,broad s, H-3), 1.18 (3H, d, J=6.5, H-2'), 1.0 (9 H, s, t-Bu), 0.31 (6H,s, di-CH₃).

I. Preparation of (1'R,3S,4R and 1'S,3R,4S)1'(t-Butyldimethylsilyl)-3-1'-acetoxy-1'-ethyl)-4-tritylthio-2-azetidinone(Isomer B) ##STR82##

A solution of (1'R,3S,4S and 1'S 3R 4S)1-(t-butyldimethylsilyl)-3-(1'-hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone(13.85 g, 27.5 mmol) in pyridine (75 ml) acetic anhydride (50 ml)(prepared at 0°) was stirred at room temperature for 40 h. The reagentswere evaporated off (the last traces being removed azeotropically withtoluene 3 times) leaving a nearly white solid. Crude derivative wascrystallized from an ether-petroleum ether mixture to give pure titlecompound (97.5%). ¹ Hmr (CDCl₃ ν: 7.64-7.03 (15H, m, H aromatic), 4.60(1H, m, J=6, H-1'), 3.92 (1H, d, J=2, H-4), 3.55 (1H, dd, J=2, J=6,H-3), 1.79 (3H, s, CH₃ CO), 0.98 (3H, d, J=6, CH.sub. 3), 0.88 (9H, s,t-butyl), 0.12 (6H, s, CH₃); ir (CHCl₃) ν_(max) : 1775, 1740 cm⁻¹ (C═O).

J. Preparation of1-(t-Butyldimethylsilyl)-3-(1'-paranitrobenzyldioxycarbonyl)-1'-ethyl)-4-tritylthio-2-azetidinone(4 isomers) ##STR83## "Isomer C"

n-Butyllithium (8.8 ml of 1.6M solution in hexane, 14 mmol; just enoughto obtain a permanent pink coloration) was added dropwise to a solutionof "Isomer C" of1-(t-butyldimethylsilyl)-3-(1'-hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone(6.55 g, 13 mmol) in THF (70 ml) maintained at -78° C. After a 15 minstirring period a solution of paranitrobenzyl chloroformate (3.2 g, 14.8mmol) in THF (30 ml) was added dropwise. The mixture was stirred 1 h at-78° C. and poured into an ammonium chloride solution (100 ml).Extraction with ethyl acetate (3×100 ml) washing with brine, drying andconcentration left 11 g of crude material. The pure title compound wasobtained by chromatography on silica gel (220 g) eluting with increasingamounts of ether in benzene. 93%, mp 118°-9° C. (ether); ¹ Hmr (CDCl₃)δ: 8.35-7 (19H, m, aromatics), 5.12 (2H, s, benzyl), 4.08 (1H, d, J=1.8,H- 4), 4-3.5 (1H, dq, J=6.5, J=2, H-1'), 3.10 (1H, dd, J=2, J=1.8, H-3),1.2 (3H, d, J=6.5, CH₃), 1.0 (9H, s, Bu) and 0.30 ppm (6H, 2s, CH₃); ir(CHCl₃) ν_(max) : 1745 cm⁻¹ (C═O); Anal. calcd for C₃₈ H₄₂ N₂ O₆ SiS: C66.83, H 6.20, N 4.10, S 4.69; found: C 66.90, H 6.26, N 4.11, S 4.59.

"Isomer B"

The "Isomer B" of1-(t-butyldimethylsilyl)-3-(1'-hydroxy-1'-ethyl(-4-tritylthio-2-azetidinone,treated as described above gave pure "Isomer B" of1-(t-butyldimethylsilyl)-3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-4-tritylthio-2-azetidinoneas a foam, 95%. ¹ Hmr (CDCl₃) δ: 8.32-6.90 (19H, m, aromatics), 5.1 (2H,s, benzyl), 4.65-4.20 (1H, m, H-1'), 3.97 (1H, d, J=1.5, H-4), 3.58 (1H,dd, J=1.5, J=5.8, H-3), 1.1 (3H, d, CH₃), 0.7 (9H, s, Bu and 0.2 ppm(6H, s, CH₃); ir (film) ν_(max) : 1755, 1740 cm⁻¹ C═O.

"Isomer A"

The "Isomer A" of1-(t-butyldimethylsilyl-3-(1'-hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone,treated as described above gave pure "Isomer A" of1-(t-butyldimethylsilyl-3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-1'-tritylthio-2-azetidinoneas an oil. 95% ¹ Hmr (CDCl₃) δ: 8.3-6.7 (19H, m, aromatics), 4.95 (2H,ABq, benzyl), 4.53 (1H, p, J=7.5, J=7.5, H-1'), 4.31 (1H, d, J=6, H-4),3.32 (1H, dd, J=6, J=7.5, H-3), 1.44 (3H, d, J=6.5), 0.95 (9H, s, tBu)and 0.2 ppm (6H, 2s, CH₃).

"Isomer D"

Likewise "Isomer D" of1-(t-butyldimethylsilyl-3-(1'-hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone,gave pure "Isomer D" of1-(t-butyldimethylsilyl)-3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-4-tritylthio-2-azetidinone,90%. ¹ Hmr (CDCl₃) δ: 8.3-6.7 (19H, m, aromatics), 5.20 (2H, ABq,benzyl), 4.72 (1H, d, J=5, H-4), 3.50 (1H, dq, J=6.5, J=0.5, H-1'), 2.85(1H, dd, J=0.5, J=5, H-3), 1.03 (3H, d, J=6.5, CH₃), 1.0 (9H, s, t-Bu)and 0.35 ppm (6H, s, CH₃); mp 130°-2° C. Anal. calcd for C 66.83, H6.20, N 4.10, S 4.70; found: C 66.56, H 6.28, N 3.96, S 4.89.

K. Preparation of (1'S,3S,4R and 1'R,3R,4S)1-(t-Butyldimethylsilyl)-3-(1'-methanesulfonyloxy-1'-ethyl)-4-tritylthio-2-azetidinone(Isomer C) ##STR84##

A solution of (1'S,3S,4R and1'R,3R,4S)-1-(t-butyldimethylsilyl)-3-(1'-hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone(Isomer C) (2.0 g, 4 mmol) in dichloromethane (80 ml) was treated at 5°C., with methanesulfonyl chloride (0.99 g, 8.6 mmol) and triethylamine(0.87 g, 8.6 mmol). After stirring at that temperature for 1 h under N₂,the solution was washed with brine, dried (MgSO₄) and evaporated todryness. After crystallization from ether-pet-ether, 1.9 g (81.9%) ofmesylate was obtained. mp 120°-22° C.; ¹ Hmr (CDCl₃) δ: 7.13-7.61 (15H,m, aromatics), 4.50 (1H, d, J=2, H-4), 3.62 (1H, dq, J=6.5, 2, H-1'),2.96 (1H, dd, J=2, 2, H-3), 2.84 (3H, s, methanesulfonyl), 1.22 (3H, d,J=6.5, H-2'), 0.99 (9H, s, Si-t-Bu) and 0.30 ppm (6H, s, Si-(CH₃)₂); irν_(max) (CHCl₃): 1746 (C═O), 1343 and 1180 cm⁻¹ (SO₂).

L. Preparation of (1'R,3S,4R and 1'S,3R,4S)1-(t-Butyldimethylsilyl)-3-(1'-methanesulfonyloxy-1'-ethyl)-4-tritylthio-2-azetidinone(Isomer B) ##STR85##

A solution of (1'R,3S,4R and 1'S,3R,4S)1-(t-butyldimethylsilyl)-3-(1'-hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone(Isomer B) (5.03 g, 10 mmol), methanesulfonylchloride (2.52 g, 22.0mmol) and triethylamine (2.23 g, 22.0 mmol) in CH₂ Cl₂ (200 ml) wasstirred at 5° C. for 1 h. Then the solution was washed with brine, dried(MgSO₄) and evaporated to leave a residue which crystallized as a whitesolid when triturated in ether (5.40 g, 93%) mp 127°-31° C. ¹ Hmr(CDCl₃) δ: 7.20-7.63 (15H, m, aromatics), 4.51 (1H, dq, J=5.0-6.2,H-1'), 4.10 (1H, d, J=2.0, H-4), 3.60 (1H, dd, J=5.0-2.0, H-3), 2.03(3H, s, --CH₃), 1.01 (3H, d, J=6.2, H-2'), 0.90 (9H, s, t-Bu), 0.12 (6H,s, --CH₃); ir (CHCl₃) ν_(max) : 1745 cm⁻¹ (C═O).

M. Preparation of (1'S,3S,4R and 1'R,3R,4S)3-(1'-p-Bromobenzenesulfonyloxy-1'-ethyl)-1-(t-butyldimethylsilyl)-4-tritylthio-2-azetidinone(Isomer C) ##STR86##

A solution of (1'S,3S,4R and 1'R,3R,4S)1-(t-butyldimethylsilyl)-3-(1'-hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone(Isomer C) (2.5 g, 5 mmol) in dry THF (100 ml) was cooled to -78° C. andtreated with 2.52M butyllithium/hexane (2.38 ml, 6 mmol). After 3-4 minp-bromobenzenesulfonylchloride (1.53 g, 6 mmol) dissolved in THF wasadded dropwise. The solution was stirred at -78° C. for 3 h and thenallowed to come to room temperature. Then the solvent was evaporated andthe desired product purfied by column chromatography (silica gel, CH₂Cl₂) (3.36 g, 94.6%) mp 142°-44° C.; ¹ Hmr (CDCl₃) δ: 7.68 (4H, s,benzenefulsonyl), 7.28-7.60 (15H, m, aromatics), 4.59 (1H, d, J=1.8,H-4), 3.68 (1H, dq, J=6.2, H-1'), 2.99 (1H, dd, J=1.8, 2.0, H-3), 1.18(3H, d, J=6.2, H-2'), 1.08 (9H, s, t-Bu), 0.40 and 0.38 (6H, 2S, --CH₃);ir (CHCl₃) ν_(max) : 1749 cm⁻¹ (C═O).

N. Preparation of (1'S,3R,4R and 1'R,3S,4S)3-(1'-Methoxymethyl-1'-ethyl)-4-tritylthio-2-azetidinone (isomer A)##STR87##

A cold (0° C.) HMPA-H₂ O (116 ml-13 ml) solution of Isomer A of1-(t-butyldimethylsilyl)-3-(1'-methoxymethyl-1'-ethyl)-4-tritylthio-2-azetidinone(11 g, 20 mmol) was treated with sodium azide (2.7 g, 42 mmol). The coldbath was removed and the mixture was stirred for 30 min. It was thenpoured into cold water (1.3 l) and dried. The title compoundrecrystallized from ethyl acetate-hexanes (7.2 g, 83%) as a white solidmp 173°-174° C. ¹ Hmr (CDCl₃) δ: 7.10-7. (15H, m, aromatics), 4.85 (2H,ABq, J=7.4, O--CH₂ --O), 4.53 (1H, d, J=5.2, H-4), 4.42 (1H, s, N-H),4.15 (1H, m, H-1'), 3.5 (1H, m, H-3), 3.47 (3H, s, O--CH₃ ), 1.5 (3H, d,J=6, CH₃). ir (KBr) ν_(max) : 3400-3500 (N-H) and 1760 cm⁻¹ (C═O).

O. Preparation of (1'S,3S,4R and 1'R,3R,4S)3-(1'-Methoxymethyloxy-1'-ethyl)-4-tritylthio-2-azetidinone (Isomer C)##STR88##

A cold (dry ice-acetone bath) solution of (1'S,3S,4R and 1'R,3R,4S)1-(t-butyldimethylsilyl)-3-(1'-hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone(5.03 g, 10 mmol) in THF (50 ml, distilled over LAH) was treateddropwise with a 1.6M solution of n-butyl lithium in hexane (13.0 ml)until a pink coloration persisted. A THF (20 ml) solution of bromomethylmethylether (1.49 g, 0.97 ml, 1.19 mmol) was added dropwise. The mixturewas stirred at -78° C. for 30 min and for a 3 h period at 0° C. It waspoured in an ice cold ammonium chloride solution and extracted withether. The ether extracts were combined, washed with water, dried(MgSO₄) and concentrated to give crude (1'S,3S,4R and 1'R,3R,4S)1-(t-butyldimethylsilyl)-3-(1'-methoxymethyloxy-1'-ethyl)-4-tritylthio-2-azetidinone(5.83 g, 100%) which was deprotected as described below:

A cold (ice bath) solution of the above derivative (5.83 g, 10 mmol) inHMPA-H₂ O (90 ml-10 ml) was treated with sodium azide (1.365 g, 21mmol). The cooling bath was removed and the mixture was stirred at roomtemperature for a 2 h period. It was then poured slowly into ice coldwater (900 ml) and stirred for 30 min. The precipitate was collected byfiltration and redissolved in methylene chloride. The solution waswashed with water and brine and dried (MgSO₄) to give the title compound(3.0 g, 69.3%), mp 172-2.5 (ethyl acetate-hexane); ir (CHCl₃) ν_(max) :3400 (N-H) and 1760 cm⁻¹ (C═O); ¹ Hmr (CDCl₃) δ: 7.67-7.12 (15H, m, Haromatics), 4.63 (2H, center of ABq, J=6, O--CH₂ --O), 4.49 (1H, s,N-H), 4.40 (1H, d, J=3, H-4), 4.25-3.80 (1H, m, H-1'), 3.35-3.15 and3.26 (4H, s+m, CH₃ and H-3) and 1.30 ppm (3H, d, J=6, CH₃).

P. Preparation of (1'R,3S,4R and 1'S,3R,4S)3-(1'-Formyloxy-1'-ethyl)-4-tritylthio-2-azetidinone (Isomer B)##STR89##

A solution of (1'S,3S,4R and 1'R,3R,4S)3-(1'-p-bromobenzenesulfonyloxy-1'-ethyl)-1-(t-butyldimethylsilyl)-4-tritylthio-2-azetidinone(Isomer C) in DMF (3 ml) was heated at 50° C. for 48 h and then at 100°C. for 4 h. The reaction mixture was then diluted with H₂ O andextracted with ether. The ethereal extracts were washed with brine,dried (MgSO₄) and evaporated. The title compound was obtained as whitecrystals after purification by column chromatography (silica gel, 5% CH₃CN--CH₂ Cl₂) (2 mg, 4.8%) mp 131°-32° C.; ¹ Hmr (CDCl₃) δ: 8.07 (1H, s,CHO), 7.24-7.56 (15H, m, aromatics), 5.23 (1H, dq, J=6.4, 7, H-1'), 4.38(1H, dm J=2.4, H-4), 4.25 (1H, s, NH), 3.20 (1H, dd, J=7, 2.4, H-3),1.43 (3H, d, J=6.4, H-2'); ir (CHCl₃) ν_(max) : 3400 (NH), 1765 (C═O),1725 cm⁻¹ (C═O).

Q. Preparation of (1'R,3S,4R and 1'S,3R,4S)3-(1'-Acetoxy-1'-ethyl)-4-tritylthio-2-azetidinone (isomer B) ##STR90##

Pure derivative (1'R,3S,4R and 1'S,3R,4S)1-(t-butyldimethylsilyl)-3-(1'-acetoxy-1'-ethyl)-4-tritylthio-2-azetidinone(5.77 g, 10.57 mmol) was dissolved in warm HMPT-water (60 ml, 10 ml).The solution was cooled down at room temperature and NaN₃ (1.2 g wasadded in. It was stirred for 45 min (reaction progression was followedby tlc) and poured slowly in stirred cold water (800 ml). The mixturewas stirred for 20 more min. The crystalline material was collected andwashed with water. It was redissolved in CH₂ Cl₂, washed with water(twice) and brine and dried over MgSO₄. Solvent evaporation left a foamwhich crystallized out from ether-petroleum ether (4.90 g, 96.5%, mp143°-44.5° C.).

ir (CH₂ Cl₂)ν_(max) : 3395 (N-H), 1772, 1738 cm⁻¹ (C═O). ¹ Hmr (CDCl₃)δ: 7.9-6.8 (15H, m, H aromatic), 5.12 (1H, center of dq, J=6.5, 7.5,H-1'), 4.33 (1H, d, J=2.8, H-4), 4.20 (1H, bs, N-H), 3.17 (1H, ddd,J_(3-1') =7.5, J₃₋₄ =2.8, J_(3-NH) =1, H-3), 2.1 (3H, s, CH₃ CO), 1.35(3H, d, J-6.5, CH₃).

R. Preparation of 3-(1'-Hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone.Mixture of four isomers) ##STR91##

A solution of lithium diisopropyl amide¹ (0.74 mmol) was prepared at-78° C. in dry tetrahydrofuran (5 ml) from diisopropyl amine (0.103 ml,0.74 mmol) and BuLi (0.29 ml of a 2.52M in hexane). After 30 min at -78°C., a solution of the (R and S)1-trimethylsilyl-4-tritylthio-2-azetidinone (0.292 g, 6.99 mmol) in drytetrahydrofurane (2 ml) was added dropwise. After 5 min, excess offreshly distilled acetaldehyde (0.2 ml) was added all at once. After 20min at -78° C., tlc indicated complete disappearance of startingmaterials and the reaction mixture was quenched by adding to a saturatedsolution of ammonium chloride. Extraction with ethyl acetate (2×25 ml)followed by washing of the combined organic phases with saturated NH₄Cl, brine and drying on anhydrous magnesium sulfate gave, afterevaporation of the solvent, a yellow oil. Filtration of this oil onsilica gel (10 g, elution C₆ H₆ :EtOAc, 6:4) gave a mixture of alcohols(0.215 g, 80%). This mixture (¹ Hmr) cannot be separated either by hplcor by tlc.

a: Acetylation

Acetylation of an aliquot of the mixture (0.065 g) with excess aceticanhydride (1.0 ml) and pyridine (1.4 ml) gave a mixture of acetates.hplc Analysis indicated four components² : (a) 34:6%; (b) 17.4%; (c)30.1%; (d) 17.9%. Compound (a) was identical to the isomer B by directcomparison (hplc).³

b: t-Butyldimethyl silyl derivatives

The mixture of alcohols (0.121 g, 0.34 mmol) was treated with t-butyldimethylchlorosilane (0.117 g, 0.776 mmol) and triethyl amine (0.10 ml,7.14 mmol) in dry dimethylformamide (1 ml) for 36 h at room temperature.After dilution with ethyl acetate, the solution was washed withsaturated ammonium chloride and dried over anhydrous magnesium sulfate.Evaporation gave an oil (0.716 g) which contains 4 components by HPLC.a=3.7%; b=60.6%; c=31.1%; d=4.6% (the identity of each one has not beenestablished)⁴.

NOTE:

S. Preparation of (1'R,3S,4R and 1'S,3R,4S)3-(1'-Benzoxy-1'-ethyl)-4-tritylthio-2-azetidinone (Isomer B) ##STR92##

A solution of (1'S,3S,4R and 1'R,3R,4S)3-(1'-methanesulfonyloxy-1'-ethyl)-4-tritylthio-2-azetidinone (Isomer C)(035 mg, 2 mmol) and sodium benzoate (432 mg, 3 mmol) in 10% H₂ O-DMF(10 ml) was heated at 90° C. for 7.5 h. Then the reaction mixture wasdiluted with H₂ O and extracted with ethyl acetate. The organic extractswere washed with brine, dried (MgSO₄) and evaporated. The residue,purified by column chromatography (silica gel, 5% CH₃ CN AM--CH₂ Cl₂)gave the title compound as a white solid (108 mg, 23.2%) mp 158° C. ¹Hmr (CDCl₃) δ: 7.03-8.25 (20H, m, aromatics), 5.32 (1H, dq, J=6.1, 9,H-1'), 4.40 (1H, d, J=2.5, H-4), 4.30 (1H, s, N-H), 3.40 (1H, dd, J=9,2.5, H-3), 1.50 (3H, d, J=6.1, H-2'); ir (CHCl₃) ν_(max) : 3400 (N-H),1765 (C-O), 1715 cm⁻¹ (C═O).

T. Preparation of3-(1'-Paranitrobenzyldioxycarbonyl-1'-ethyl)-4-tritylthio-2-azetidinone(4 isomers) ##STR93## "Isomer C"

(a) A solution of "Isomer C" of1-(t-butyldimethylsilyl)-3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-4-tritylthio-2-azetidinone(1.3 g) in a mixture of TFA (5 ml), water (5 ml), dichloromethane (20ml) and methanol (30 ml) was stirred for 2 days at room temperature. Thesolution was diluted with water and the aqueous phase extracted withdichloromethane. The combined organic phases were washed with sodiumbicarbonate and water, dried and concentrated to leave an oil.Crystallization from ether gave the pure title compound (902 mg), mp78°-80° C.; ¹ Hmr (CDCl₃): 8.25-6.75 (19H, m, aromatics), 5.21 (2H, s,benzyl), 5.05 (1H, m, H-1'), 4.40 (1H, s, N-H), 4.27 (1H, d, J=2.8,H-4), 3.37 (1H, dd, J=5.3, 2.8, H-3) and 1.37 ppm (3H, d, J=6.5, CH₃);ir (CHCl₃) ν_(max) : 3390 (N-H), 1765 and 1745 (shoulder) (C═O, and 1525cm⁻¹ (NO₂).

(b) A cold (0° C.) HMPT-H₂ O (90 ml-19 ml) solution of "Isomer C" of1-(t-butyldimethylsilyl)-3-(1'-paranitrobenzyldioxycarboxyl-1'-ethyl)-4-tritylthio-2-azetidinone(9.11 g, 13.3 mmol) was treated with sodium azide (1.82 g, 27.9 mmol).The cold bath was removed and the mixture was stirred for 30 min. It wasthen poured into water (1 l) and extracted with ether (5×200 ml). Theether fractions were combined and washed with water (5×200 ml), brineand dried over MgSO₄. Alternatively since the title compoundprecipitated out on water dilution, it was filtered off andrecrystallized from ether; 7.22 g, 89%, mp 78°-80° C.

"Isomer B"

"Isomer B" of3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-4-tritylthio-2-azetidinonewas prepared as described above for the "Isomer C"; 92%; mp 155.5°-6° C.(ether); ¹ Hmr (CDCl₃) δ: 8.25-6.80 (19H, m, aromatics), 5.20 (2H, s,benzyl), 4.95 (1H, m, H-1'), 4.35 (1H, d, J=2.9, H-4), 4.17 (1H, s,N-H), 3.20 (1H, dd, J=10.8, J=2.9, H-3) and 1.40 ppm (3H, d, J=7.5,CH₃); ir (CHCl₃) ν_(max) : 3480, 3390 (N-H), 1772, 1750 (C═O), and 1525cm⁻¹ (NO₂). Anal. calcd for C₃₂ H₂₈ N₂ O₆ S: C 67.59, H 4.96, N 4.93, S5.64; found: C 67.48, H 4.98, N 4.92, S 5.67.

"Isomer A"

"Isomer A" of3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-4-tritylthio-2-azetidinonewas prepared as described above for the "Isomer C"; mp 205°-6° C. ¹ Hmr(CDCl₃) δ: 8.2-6.7 (19H, m, aromatics), 5.22 (2H, ABq, benzyl),5.57-4.85 (1H, m, H-1'), 4.65 (1H, N-H), 4.50 (1H, d, J=6.5, H-4), 3.65(1H, dd, J=6.5, 12, J_(N-H) =1, H-3) and 1.52 ppm (3H, d, J=7.5).

"Isomer D"

"Isomer D" of3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-4-tritylthio-2-azetidinonewas prepared as described above for "Isomer C"; ¹ Hmr (CDCl₃) δ:8.15-6.70 (19H, m, aromatics), 5.23 (2H, ABq, benzyl), 5.20 (1H, m,H-1'), 4.75 (1H, NH), 4.52 (1H, d, J=5.5, H-4), 3.42 (1H, J=5.5, 3, H-3and 1.5 ppm (3H, d, J=6.5, CH₃). (J value for H-3 taken after D₂ O.exchange).

U. Preparation of (1'R,3S,4R and 1'S,3R,4S)3-(1'-ethanesulfonyloxy-1'-ethyl)-4-tritylthio-2-azetidinone (isomer B)##STR94##

A solution of (1'R,3S,4R and 1'S,3R,4S)1-(t-butyldimethylsilyl)-3-(1'-methanesulfonyloxy-1'-ethyl)-4-trithylthio-2-azetidinone.(Isomer B) (4.95 g, 8.5 mmol) and sodium azide (1.11 g, 17.0 mmol) in10% H₂ O-HMPA (50 ml) was stirred at room temperature for 30 min. Thenthe solution was diluted with water (250 ml) and extracted with ether.The organic extracts were washed with brine, dried (MgSO₄) andevaporated. Crystallization of the residue (ether-petether) gave thetitle compound (3.33 g, 83.8%). mp 130°-31° C. ¹ Hmr (CDCl₃) δ:7.20-7.62 (15H, m, aromatics), 4.97 (1H, dq, J=6.4, 6.1, H-1'), 4.56(1H, d, J=2.8, H-4), 4.22 (1H, m, N-H), 3.27 (1H, dd, J=6.1, 2.8, H-3 ),3.0 (3H, s, --CH₃), 1.63 (3H, d, J=6.4, H-2'); ir (nujol) ν_(max) : 3195(n-H), 1768 cm⁻¹ (C═O).

V. Preparation of (1'S,3S,4R and1'R,3R,4S)3-(1'-ethanesulfonyloxy-1'-ethyl)-4-tritylthio-2-azetidinone(Isomer C) ##STR95##

A solution of (1'S,3S,4R and1'R,3R,4S)1-(t-butyldimethylsilyl)-3-(1'-methanesulfonyloxy-1'-ethyl)-4-tritylthio-2-azetidinone(isomer C) (2.85 g; 4.9 mmol) in 10% aqueous HMPA (25 ml) was treatedwith sodium azide (0.65 g, 10 mmol) and stirred at 25° C. for 0.5 h. Bydiluting the solution with water (250 ml), the reaction product wasforced to crystallize out. The crude mesylate was redissolved indichloromethane, washed with brine, dried (MgSO₄) and evaporated.Trituration in ether gave the title compound as white crystals mp155°-60° C.; 1.80 g; 78.6%; ¹ Hmr (CDCl₃) δ: 7.43 (15H, m, aromatic),5.02 (1H, dq, J=6.9, 4.9, H-1'), 4.55 (1H, s, N-H), 4.95 (1H, d, J=3,H-4), 3.33 (1 H, dd, J=4.9, 3, H-3), 1.51 (3H, d, J=6.9, H-2'); irν_(max) : 3395 (N-H), 1768 cm⁻¹ (C═O); Anal. calcd for C₂₅ H₂₅ NO₄ S. C64.22, H 5.39, N 3.00; found: C 63.93, H 5.39, N 3.24%.

W. Preparation of (1'S,3S,4R and 1'R,3R,4S)3-(1'-p-Bromobenzenesulfonyloxy-1'-ethyl)-4-tritylthio-2-azetidinone(Isomer C) ##STR96##

A solution of (1'S,3S,4R and 1'R,3R,4S)3-(1'-p-bromobenzenesulfoxyloxy-1'-ethyl)-1-(t-butyldimethylsilyl)-4-tritylthio-2-azetidinone(Isomer C) (1.42 g, 2 mmol) and sodium benzoate (0.865 g, 6 mmol) in 10%H₂ O-HMPA (40 ml) was stirred at room temperature for 1 h. Then thesolution was diluted with H₂ O (100 ml) and extracted with ether. Theether extracts were washed with brine, dried (MgSO₄) and evaporated. Thecrude crystalline title compound was triturated in a small volume ofether and collected by filtration (0.92 g, 77%) mp 125°-26° C. ¹ Hmr(CDCl₃) δ: 7.80 (4H, s, benzenesulfonyl), 7.30-7.65 (15H, m, aromatics),5.13 (1H, dq, J=6.5, 4.0, H-1'), 4.50 (1H, d, J=2.9, H-4), 4.40 (1H, s,N-H), 3.40 (1H, dd, J=4.0, 2.9, H-3), 1.50 (3H, d, J=6.5, H-2'); ir(CHCl₃) ν_(max) : 3400 cm⁻¹ (N-H), 1770 cm.sup. -1 (C═O).

X. Preparation of (1'R,3S,4R and 1'S,3R,4S)3-(1'-Hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone (Isomer B) ##STR97##

To a warm solution of (1'S,3S,4R and 1'R,3R,4S)3-(1'-p-bromobenzenesulfonyloxy-1'-ethyl)-1-(t-butyldimethylsilyl)-4-tritylthio-2-azetidinone(Isomer C) in HMPA (5 ml) was added dropwise 12 ml of H₂ O. The reactionmixture was kept at 90° C. for 20 h, then diluted with ether and washed4 times with brine. The organic solution was dried (MgSO₄), evaporatedand the crude title compound purified by column chromatography (silicagel, 15% CH₃ CN--CH₂ Cl₂). A white solid was obtained (122 mg, 44.5%) mp187°-189° C. which was found to be identical to a sample of the titlecompound prepared by another method.

Y. Preparation of 3-(1'-Hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone##STR98##

Both isomers, (1'S,3S,4R and 1'R,3R,4S)3-(1'-hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone (Isomer C) and(1'R,3S,4R and 1'S,3R,4S)3-(1'-hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone (Isomer B) wereprepared by the same method. For example, a solution of (1'S,3S,4R and1'R,3R,4S)1-(t-butyldimethylsilyl)-3-(1'-hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone(Isomer C) (1.0 g, 2 mmol) and sodium benzoate (0.865 g, 6 mmol) in 10%H₂ O-DMF (40 ml) was stirred at room temperature for 18 h. Then thereaction mixture was diluted with H₂ O and extracted with ether. Theorganic extracts were washed with brine, dried (MgSO₄) and evaporated.The crude title compound was crystallized from cold ether (0.47 g, 61%)mp 134° -35° C. ¹ Hmr (CDCl₃) δ: 7.12-7.56 (15H, m, aromatics), 4.48(1H, s, N-H), 4.28 (1H, d, J=2.8, H-4), 2.94 (1H, dq, J=6.5, 6.2, H-1'),3.06 (1H, dd, J=6.2, 2.8, H-3), 2.18 (1H, s, --OH), 1.30 (3H, d, J=6.5,H-2'); ir (CHCl₃) ν_(max) : 3400 (n-H), 1760 cm⁻¹ (C═O). Similarly(1'R,3S,4R and 1'S,3R,4S)1-(t-butyldimethylsilyl)-3-(1'-hydroxy-1'-ethyl)-4-tritylthio-2-azetidinone(Isomer B) mp 190°-92° C. ¹ Hmr (CDCl₃) δ: 7.10-7.55 (15H, m,aromatics), 4.45 (1H, d, J=2.5, H-4), 4.28 (1H, s, NH), 4.10 (1H, dq,J=6.4, 5.3, H-1'), 3.08 (1H, dd, J=5.3, 2.5, H-3), 1.50 (1H, s, --OH),1.30 (3H, d, J=6.4, H-2'); ir (CHCl₃) ν_(max) : 3400 (N-H), 1760 cm⁻¹(C═O).

Z. Preparation of (1'S,3R,4R and 1'R,3S,4S)3-(1'-Methoxymethyl-1'-ethyl)-1-(paranitrobenzyl2"-hydroxy-2"-acetate)-4-tritylthio-2-azetidinones (Isomer A) ##STR99##

A mixture of Isomer A of3-(1'-methoxymethyl-1'-ethyl)-4-tritylthio-2-azetidinone (7.5 g, 17.3mmol), paranitrobenzyl glyoxylate hydrate (4.7 g, 20.8 mmol) and toluene(300 ml) was heated under reflux for 1 h in a Dean and Stark apparatusfilled with 3 Å molecular sieves. The solution was cooled in ice andtriethylamine (0.24 ml, 1.7 mmol) was added dropwise. The mixture wasstirred for 1 h, washed with diluted hydrochloric acid, sodiumbicarbonate and brine, dried and concentrated to give the title compoundas a foam (10.5 g, 94%). ¹ Hmr (CDCl₃) δ: 8.25-6.84 (19H, m, aromatics),5.24 (2H, s, benzyls), 4.67-4.83 (3H, m, O-CH₂ and H-4), 4.34-4.55 (1H,m, H-2"), 4.02 (1H, m, H-1'), 3.54 (1H, m, H-3), 3.40 (3H, s, O-CH₃),1.38 (3H, d, J=6.5, CH₃); ir (KBr) ν_(max) : 3360 (OH), 1770 (C═O ofβ-lactam), 1735 (C═O of ester) and 1605 cm⁻¹ (aromatics).

AA. Preparation of (1'S,3S,4R and 1'R,3R,4S)3-(1'-Methoxymethoxy-1'-ethyl)-1-(paranitrobenzyl2"-hydroxy-2"-acetate)-4-tritylthio-2-azetidinone (Isomer C) ##STR100##

A solution of hydrated paranitrobenzyl glyoxylate (1.73 g, 7.11 mmol)was refluxed in toluene (90 ml) using a Dean Stark condenser filled with3 Å molecular sieves for a 2 h period. To the boiling solution was added(1'S,3S,4R and 1'R,3R,4S)3-(1'-methoxymethyloxy-1'-ethyl)-4-tritylthio-2-azetidinone (3.0 g, 6.93mmol) and the mixture was refluxed for 2 h more. The mixture was cooledto room temperature, triethyl amine (70 mg, 97 μl, 0.69 mmol) was addedand it was stirred for 2 h. The reaction mixture was diluted with ether,washed with 1% aqueous HCl, water, 1% aqueous NaHCO₃, water and brine,dried (MgSO₄) and concentrated to give the title compound (4.60 g,100%); ir (CHCl₃) ν_(max) : 3530-3100 (O-H), 1765, 1750 (C═O) and 1525cm⁻¹ (NO₂); ¹ Hmr (CDCl₃) δ: 8.22, 8.18 (2H, 2d, J=8, Hm aromatics),7.67-7.0 (17H, m, H-aromatics), 5.3 (2H, bs, CH₂ -PNB), 5.30-5.02 (m,H-2"), 4.89-4.52 (m, H-1' and O-H), 4.63, 4.59 (1H, 2d, J= 2, H-4),4.33, 4.30 (2H, 2 center of 2 ABq, J=7, J=7, O--CH₂ --O), 4.1-3.67 (1H,m, H-1'), 3.2 (1H, H-3), 3.1, 3.6 (3H, 2s, CH₃ -O), and 1.15 ppm (3H, d,J=6.5, CH₃).

BB. Preparation of (1'R,3S,4R and 1S,3R,4S)3-(1'-Acetoxy-1'-ethyl)-1-(paranitrobenzyl-2"-hydroxy-2"-acetate)4-tritylthio-2-azetidinone##STR101## "Isomer B"

A solution of hydrated p-nitrobenzyl glyoxylate (triturated with ether)(1.82 g, 30 mol) was refluxed in benzene through a Dean Stark condenserfilled with 3 Å molecular sieves for 2 h. To that was added azetidinone(1'R,3S,4R and 1'S,3R,4S)3-(1'-acetoxy-1'-ethyl)-4-tritylthio-2-azetidinone (10.88 g, 25.2 mmol)and the mixture was refluxed for 1 h more. The solution was cooled atroom temperature and triethyl amine (0.35 ml, 2.5 mmol was added. It wasthen stirred for 2 h; the reaction progression being followed by tlc.*Solvent evaporation afforded a white foam in quantitative yield (100%,mixture of epimers) *Alternatively the solution can be acid and basewashed. ir (CH₃ Cl₂) ν_(max) : 3520 (OH), 1775, 1745 cm⁻¹ (C═O); ¹ Hmr(CDCl₃)δ: 8.2, 8.18 (2H, 2d, J=8, Ho aromatic), 7.80-6.90 (17H, m,H-aromatic), 5.28, 5.17 (2H, 24, CH₂ -PNB, 4.89 (0.67H, d, J=7.2, CHO),4.80 (center of m, H-1'), 4.38 (0.33 H, 2d, J=8.8, CHO), 4.22 (D.33H, d,J₄₋₃ =2.5, H-4), 4.09 (0.67H, d, J₄₋₃ =2.1, H-4), 3.65 (D.67H, dd,J_(3-1') =5.8, J₃₋₄ =2.1, H-3), 3.47 (0.33H, dd, J_(3-1') =5.5 J₃₋₄=2.5, H-3), 3.33 (0.33H, d, J=8.8, OH), 3.23 (0.67H, d, J=7.5, OH),1.38, 1.86 (3H, 2s, CH₃ CD), 1.10, 1.06 (3H, 2d, J=5.8, 6.3, CH₃).

CC. Preparation of3-(1'-Paranitrobenzyldioxycarbonyl-1'-ethyl)-1-(paranitrobenzyl2"-hydroxy-2"-acetate)4-tritylthio-2-azetidinone (4 isomers) ##STR102##"Isomer C"

A mixture of "Isomer C" of3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-4-tritylthio-2-azetidinone(1.70 g, 0.3 mmol), paranitrobenzyl glyoxylate hydrate (815 mg, 3.6mmol) and toluene (50 ml) was heated under reflux 7 days in a Dean andStark apparatus filled with 3 Å molecular sieves. The cooled solutionwas washed with dilute hydrochloric acid, sodium bicarbonate and brine,dried and concentrated to give the title compound (2.1 g) as an epimericmixture at carbon-2". Purification was effected by chromatography oversilica gel. Alternatively the title compound could be prepared by usinga catalytic amount of triethyl amine. Less polar epimer at 2": ¹ Hmr(CDCl₃) δ: 8.25-6.80 (23H, m, aromatics), 5.30 and 3.12 (4H, 2s,benzyls), 4.65 (1H, d, J=9, H-2"), 4.45 (1H, d, J=2.5, H-4), 4.45-4.10(1H, m, H-1'), 3.50 (1H, d, J=9, 2"-OH), 3.28 (1H, dd, J=2.5, J=2.5,H-3) and 1.23 ppm (3H, d, J=6.5, CH₃); ir (CHCl₃) ν_(max) : 3530 to 3200(D-H), 1765, 1750 (C═O) and 1525 cm⁻¹ (NO₂). More polar isomer at C-2":¹ Hmr (CDCl₃) δ: 8.25-6.85 (23H, m, aromatics), 5.25 and 5.08 (4H, 2s,benzyls), 5.05 (1H, d, J=7, H-2"), 4.35 (1H, d, J=2.5, H-4), 4.40-4.05(1H, m, H-1'), 3.42 (1H, J=7, 2"-OH), 3.33 (1H, dd, J=2.5, 2.5, H-3),1.23 (3H, d, J=6.5, CH₃); ir (CHCl₃) ν_(max) : 3520 to 3200 (O-H), 1755(C═O) and 1525 cm⁻¹ (NO₂).

"Isomer B"

A mixture of hydrated paranitrobenzylglyoxylate (1.74 g, 7.66 mmol) and(1'R,3S,4R and 1'S,3R,4S)3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-4-tritylthio-2-azetidinone(3.63 g, 6.38 mmol) was refluxed in toluene (70 ml) on a Dean Starkcondenser filled with 3 Å molecular sieves for 3 h. The solution wascooled down to room temperature and triethyl amine (64.5 mg, 89 ml,0.639 mmol) was added. It was then stirred for 4 h, diluted with etherand washed with 2% aqueous HCl, water, 2% aqueous NaHCO₃, water andbrine. It was dried and concentrated to give pure title compound (5.02g, 100%). Separation of the 2 epimers was effected on preparative silicagel plate. Less polar epimer at 2": ir (CHCl₃) ν_(max) : 3500 (O-H),1772, 1750 (C═O) 1525 cm⁻¹ (NO.sub. 2); ¹ Hmr (CDCl₃) δ: 8.30-8.0 and7.65-6.80, (23H, m, aromatics), 5.27 and 5.13 (4H, 2s, benzyls), 4.71(1H, m, J=6.5, 6.5, H-1'), 4.28 (1H, d, J=2.2, H-4), 4.23 (1H, d, J=8.7,H-2"), 3.50 (1H, dd, J=2.2, 6.5, H-3), 3.28 (1H, d, J=8.7, O-H) and 1.18ppm (3H, d, J=6.5, CH₃). More polar epimer: ir (CHCl₃) ν_(max:) 3480(O-H) 1772, 1750 (C═O) and 1525 cm⁻¹ (NO₂); ¹ Hmr (CDCl₃) δ: 8.35-6.90(23H, m, aromatics), 5.15 (4H, benzyls), 4.72 (1H, d, J=7.5, H-2"0),4.90-4.50 (1H, m, J=6.5, 6.5, H-1'), 4.10 (1H, d, J=2, H-4), 3.68 (1H,dd, J=2, 6.5, H-3), 3.28 (1H, d, J=6.5, O-H) and 1.15 ppm (3H, d, J=6.5,CH₃).

"Isomer A"

The "Isomer A" of3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-4-tritylthio-2-azetidinonelikewise gave a mixture of "Isomer A" of3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-1-(paranitrobenzyl2"-hydroxy-2"-acetate)-4-tritylthio-2-azetidinones. ¹ Hmr (CDCl₃) δ:8.3-6.7 (23H, m, aromatics), 5.17 (2H, benzyls), 5.0 (1H, m, H-1'), 4.9and 4.8 (1H, 2d, J=6, H-4, two epimers), 4.32 and 3.96 (1H, 2s, H-2",two epimers), 3.68 (1H, dd, J=6, 6, H-3 (and 1.47 ppm (3H, 2d, J=6.5,CH₃, two epimers).

"Isomer D"

The "Isomer D" of3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-4-tritylthio-2-azetidinonelikewise gave a mixture of "Isomer D" of3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-1-(paranitrobenzyl2"-hydroxy-2"-acetate)-4-tritylthio-2-azetidinones. ¹ Hmr (CDCl₃) δ:8.30-6.60 (23H, m, aromatics), 5.20 (4H, m, benzyls), 4.83 (1H, 2d, J=5,H=4), 5.50-4.30 (2H, m, H-1' and H-2"), 3.48 (1H, m, H-3), 3.15 (1H, m,O-H), 1.37 and 1.30 ppm (3H, 2d, CH₃).

DD. Preparation of (1'S,3S,4R and1'R,3R,4S)3-(1'-Methanesulfonyloxy-1'-ethyl)-1-(paranitrobenzyl2"-hydroxy-2"-acetate)-4-tritylthio-2-azetidinone (isomer C) (epimers atC₂ "). ##STR103##

A solution of paranitrobenzylglyoxylate hydrate (9.72 g; 42.6 mmol) inbenzene (350 ml) was refluxed for 2 h, removing the water azeotropicallyin a Dean-Stark trap. To that solution was added the (1'S,3S,4R and1'R,3R,4S)3-(1'-methanesulfonyloxy-1'-ethyl)-4-tritylthio-2-azetidinone(16.62 g, 35.5 mmol) and the reflux maintained for an additional 0.5 h.Then the reaction mixture was cooled to room temperature, treated withtriethylamine (0.5 ml; 3.5 mmol) and stirred for 3 h in order tocomplete the reaction. Evaporation of the solvent left a white foamwhich was used as such in the next step. ¹ Hmr (CDCl₃) δ: 8.12 (2H, d,J=9, Hm aromatic), 7.28 (17H, part of d,Ho aromatic, trityl), 5.28 (2H,s, --CH₂ --PNB), 4.88 (0.5 H, s, H-1"), 4.62 (1.5H, m, H-2" and H-4),4.00 (2H, m, H-1', --OH), 3.15 (1H, m, H-3), 2.73 (3H, s, mesylate and1.30 ppm (3H, d, J=6 Hz, H-2'); ir ν_(max) : 3520 (O-H), 1775 (C═O) and1765 cm⁻¹ (C═O).

EE. Preparation of (1'S,3R,4R and 1'R,3S,4S)3-(1-Methoxymethyl-1'-ethyl)-1-(paranitrobenzyl2"-chloro-2"-acetate)-4-tritylthio-2-azetidinone (Isomer A) ##STR104##

Pyridine (1.1 ml, 14.2 mmol) was added dropwise to a solution of IsomerA of3-(1'-methoxymethyl-1'-ethyl)-1-(paranitrobenzyl-2"-hydroxy-2"-acetate)-4-tritylthio-2-azetidinone(7 g, 10.9 mmol) in THF (350 ml) cooled to -15° C. Immediately afterthionyl chloride (1.0 ml, 14.0 mmol) was added dropwise and the mixturewas stirred at -15° for 0.5 h. The precipitate was removed by filtrationand washed with benzene. The combined filtrates were concentrated, theresidue dissolved in fresh benzene and the solution treated withactivated charcoal, filtered and concentrated to leave to title compoundas an oil (6.5 g, 90%), ¹ Hmr (CDCl₃) δ: 6.65-8.35 (19H, m, aromatics),5.24 (2H, s, benzyl), 3.43 (3H, s, OCH₃) and 1.42 ppm (3H, d, J=6, CH₃).

FF. Preparation of (1'S,3S,4R and 1'R,3R,4S)3-(1'-ethoxymethyloxy-1'-ethyl)-1-(paranitrobenzyl2"-chloro-2"-acetate)-4-tritylthio-2-azetidinone (Isomer C) ##STR105##

A cold (ice-MeOH bath) THF (60 ml, distilled over LAH) solution of(1'S,3S,4R and 1'R,3R,4S)3-(1'-methoxymethyloxy-1'-ethyl)-1-paranitrobenzyl2"-hydroxy-2"-acetate)-4-tritylthio-2-azetidinone (4.25 g, 6.62 mmol)was treated dropwise with pyridine (0.696 ml, 8.61 mmol) and thionylchloride (0.530 ml, 8.61 mmol). The mixture was stirred for 30 min at-15° C. The precipitate was collected by filtration and washed withbenzene. The THF-benzene solution was concentrated and the residue wasdissolved again in benzene. The resulting solution was treated withcharcoal. Removal of charcoal on a Celite pad and subsequent benzeneevaporation afforded the title compound (4.86 g, 100%); ir (CHCl₃)ν_(max) : 1770 (C═O) and 1525 cm⁻¹ (NO₂); ¹ Hmr (CDCl₃) δ: 8.15, 8.12(2H, 2d, H-aromatics), 7.70- 7.00 (17H, m, H-aromatics), 5.62, 5.02 (1H,2s, H-2"), 5.27 (2H, s, CH₂ -PNB), 4.7 (1H, d, H-4) , 4.7-3.7 (m, O--CH₂--O, H-1'), 3.5-2.8 (m, H-3), 3.12, 3.08 (3H, 2s, O--CH₃), and 1.30-0.96ppm (3H, m, CH₃).

GG. Preparation of (1'R, 3S,4R and 1'S,3R,4S)3-(1'-Acetoxy-1'-ethyl)-1-(paranitrobenzyl2"-chloro-2"acetate)-4-tritylthio-2-azetidinone ##STR106## "Isomer B"

A THF (distilled over LAH) solution of (1'R,3S,4R and 1'S, 3R,4S)3-(1'-acetoxy-1'-ethyl)-1-(paranitrobenzyl-2"-hydroxy-2"-acetate)-4-tritylthio-2-azetidinone(from 10.88 g of N-H) was treated at -15° C. (ice-methanol bath) undernitrogen atmosphere with pyridine (2.19 g, 2.24 ml, 27.7 mmol) andthionyl chloride (3.3 g, 2.02 ml, 27.7 mmol) and thionyl chloride (3.3g, 2.02 ml, 27.7 mmol). The mixture was stirred for 20 min at -15°. Thesalt was filtered off and washed with benzene. Solvent (THF+benzene)evaporation afforded a residue which was taken up in benzene (warm) andtreated with charcoal. The suspension was filtered through a celite padand solvent evaporation left a foam; ir (CH₂ Cl₂) ν_(max) : 1780, 1740cm⁻¹ (C═O) ¹ Hmr (CDCl₃ δ: 8.17, 8.21 (2H, 2d, J=8, Ho aromatic)7.76-6.88 (17H, m, H-aromatic), 5.31, 5.16, 5.12, 4.73 (3H, 4s, CH₂-PNB, CHCl), 5.12-4.55 (1H, m, H-1'), 4.35-4.25 (1H, m, H-4), 3.80-3.45(1H, m, H-3) 1.90 (3H, s, CH₃ CO), 1.12 1.07 (3H, J=6.5, CH₃).

HH. 3-(1'-Paranitrobenzyldioxycarbonyl-1'-ethyl)-1-(paranitrobenzyl2"-chloro-2"-acetate)-4-tritylthio-2-azetidinones (mixture of epimers atC2") ##STR107## "Isomer C"

Pyridine (58 mg, 0.73 mmol) was added dropwise to a solution of "IsomerC" of 3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-1-(paranitrobenzyl2"-hydroxy-2"-acetate)-3-tritylthio-2-azetidinones (470 mg, 0.6 mmol;mixture of epimers at C-2") in THF (15 ml) cooled to -15" C. Immediatelyafter thionyl chloride (86.5 mg, 0.73 mmol) was added dropwise and themixture was stirred at -15° C. for 0.5 h. The precipitate was removed byfiltration and washed with benzene. The combined filtrates wereconcentrated, the residue dissolved in fresh benzene and the solutiontreated with activated charcoal, filtered and concentrated to leave thetitle compound as an oil. 530 mg; 100%. ¹ Hmr (CDCl₃) δ: 8.7-6.8 (23H,m, aromatic), 5.53 (1H, s, H-2"), 5.30 and 5.17 (4H, 2s, benzyls), 4.52(1H, d, J=2, H-4), 4.20-3.70 (1H, m, H-1'), 3.31 (1H, dd, H-3), 1.27 and1.21 ppm (3H, 2d, J=6.5); ir (CHCl₃) ν_(max) : 1780, 1750 (C═O) and 1525cm⁻¹ (NO₂).

"Isomer B"

"Isomer B" of3-(1-paranitrobenzyldioxycarbonyl-1'-ethyl)-1-(paranitrobenzyl2"-chloro-2"-acetate)-4-tritylthio-2-azetidinones (mixture of C-2"epimers) was prepared as described above for the "Isomer C" inquantitative yield. ¹ Hmr (CDCl₃) δ: 8.25-6.90 (23H, m, aromatics),5.40-5.0 (4H, m, benzyls), 5.40-4.45 (1H, m, H-1'), 4.82 and 4.57 (1H,2s, H-2"), 4.36 and 4.31 (1H, 2d, J=2.5, H-4), 3.63 (1H, m, J=2.5,J=6.5, H-3), 1.25 and 1.18 ppm (3H, 2d, J=6.5, CH₃); ir (CHCl₃)_(max) :1780, 1750 (C═O), and 1525 cm⁻¹ (NO₂).

"Isomer A"

"Isomer A" of3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-1'-(paranitrobenzyl2"-chloro-2"-acetate)-4-tritylthio-2-azetidinones (mixture of C-2"epimers). ¹ Hmr (CDCl₃) δ: 8.30-6.80 (23H, m, aromatics), 5.45-4.80 (1H,m, H-1'), 5.18 and 5.21 (4H, 2s, benzyls), 4.87 (1H, 2d, H-4), 4.22 and3.87 (1H, 2s, H-2"), 4.05-3.40 (1H, m, H-3), 1.57 and 1.50 ppm (3H, 2d,CH₃).

"Isomer D"

"Isomer D" of3-(1"-paranitrobenzyldioxycarbonyl-1'-ethyl-1'-(paranitrobenzyl2"-chloro-2"-acetate)-4-tritylthio-2-azetidinones (mixture of C-2"epimers). ¹ Hmr (CDCl₃) δ: 8.30-6.70 (23H, m, aromatics), 5.32-5.10 (4H,m, benzyls), 5.48 and 5.30 (1H, 2s, H-2"), 4.82 (1H, d, J=5, H-4),5.30-5.20 (1H, m, H-1'), 3.15 (1H, m, H-3), 1.40 and 1.30 ppm (3H, 2d,J=6.5, CH₃); ir CHCl₃) ν_(max) : 1780, 1750 (C═O) and 1525 cm⁻¹ (NO₂).

II. Preparation of (1'S,3S,4R and1'R,3R,4S)3-(1'-Methanesulfonyloxy-1'-ethyl)-1-(paranitrobenzyl2"-chloro-2"-acetate(-4-tritylthio- 2-azetidinone (isomer C) (epimers atC₂ ") ##STR108##

To a cold solution (5° C.) of (1'S,3S,4R and1'R,3R,4S)3-(1'-methanesulfonyloxy-1'-ethyl)-1-(paranitrobenzyl2"-hydroxy-2"-acetate)-4-tritylthio-2-azetidinone (24.0 g, 35.5 mmol) indry tetrahydrofuran (350 ml) was added pyridine (3.65 g, 46.2 mmol) andthionyl chloride (5.5 g, 46.2 mmol) dropwise. After stirring for 45 min,ether (100 ml) was added to precipitate the hydrochloride salt which wasfiltered off. The filtrate was evaporated and the residue redissolved inbenzene (200 ml) and treated with charcoal. Evaporation of the solventleft a nearly white foam which was used as such in the next step. ¹ Hmr(CDCl₃) δ: 8.18 (2H, d, J=9, Hm aromatic), 7.72 (17H, m, part of d, Hoaromatic, trityl), 5.57 and 5.12 (1H, s, H-2"), 5.28 (2H, s, --CH₂ PNB),4.73 (1H, 2d, H-4), 3.21 (1H, 2dq, H-3), 2.78 (3H, 2s, mesylate and 1.21ppm (3H, 2d, H-6H₂ ; H-2'); ir ν_(max) 1779 cm⁻¹ (C═O).

JJ. Preparation of (1'S,3R,4R and 1'R,3S,4S)3-(1'-Methoxymethoxy-1'-ethyl)-1-(paranitrobenzyl2"-triphenylphosphoranylidene- 2"-acetate)-4-tritylthio-2-azetidinone(Isomer A) ##STR109##

A mixture of Isomer A of3-(1'-methoxymethoxy-1'-ethyl)-1-(paranitrobenzyl-2"-chloro-2"-acetate)-4-tritylthio-2-azetidinone(6.6 g, 10 mmol), triphenylphosphine (3.3 g, 12.5 mmol), 2,6-lutidine(1.3 ml, 11 mmol) and dioxane (140 ml) was heated under reflux for 2days. The solution was diluted with ether, washed with dilute acid (5%HCl), water, dilute sodium bicarbonate solution and brine, dried andconcentrated. The residue was purified by chromatography on silica geleluting with 10% ether in benzene. Concentration of the pertinentfractions left the title compound as a foam (1.4 g, 13.7%) ir (KBr)ν_(max) : 1750 (C═O) and 1660-1650 cm⁻¹ (C═C, aromatics).

KK. Preparation of (1'S,3S,4R and 1'R,3R,4S)3-(1'-Methoxymethyloxy-1'-ethyl)-1-(paranitrobenzyl2"-triphenylphosphoranylidene-2"-acetate)-4-tritylthio-2-azetidinone(Isomer C) ##STR110##

A dioxane (100 ml, distilled over LAH) solution of (1'S,3S,4R and1'R,3R,4S)3-(1'-methoxymethyloxy-1'-ethyl)-1-(paranitrobenzyl-2"-chloro-2"-acetate)-4-tritylthio-2-azetidinone(4.86 g, 6.62 mmol), triphenylphosphine (2.60 g, 9.93 mmol) and2,6-lutidine (770 mg, 0.837 ml, 7.20 mmol) was heated under reflux for 4h and kept in a hot bath (100° C.) for 16 h. The mixture was dilutedwith ether, washed with 1% aqueous HCl, water, 10% aqueous NaHCO₃, waterand brine and dried (MgSO₄). The solution was concentrated and theresidue filtered through a silica gel (65 g) column (5%, 10% and 20%ether-benzene) to give the title compound (2.8 g, 48%). ir (CHCl₃)ν_(max) : 1795 (C═O), 1620 and 1605 (phosphorane) and 1515 cm⁻¹ (NO₂).

LL. (1'R,3S,4R and 1'S,3R,4S)3-(1'-Acetoxy-1'-ethyl)-1-(paranitrobenzyl-2"-triphenylphosphoranylidene-2"-acetate)-4-tritylthio-2-azeditinone(Isomer B) ##STR111##

A dioxane (100 ml, freshly distilled over LAH) solution of crude(1'R,3S,4R and 1'S,3R,4S) 3-(1'-acetoxy-1'-ethyl)-1-(paranitro residuewhich was passed through a silica gel (10 times its weight) column (10%ether-benzene, ether, and ethyl acetate). The title compound wasobtained as a crystalline solid (3.1 g, 49%), mp 189°-190° (ether); ir(CHCl₃) ν_(max) : 1750 (C═O), 1620, 1605 (phosphorane) and 1522 cm⁻¹(NO₂).

Isomer C

Isomer C of3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-1-(paranitrobenzyl-2"-triphenylphosphoranylidene-2"-acetate)-4-tritylthio-2-azetidinonewas prepared as described above for isomer B. ir (CHCl₃) ν_(max) : 1750(C═O), 1610, 1620 (phosphorane) and 1520 cm⁻¹ (NO₂); ¹ Hmr (CDCl₃) δ:8.6=6.7 (H, aromatics), 5.22 and 4.95 (benzyls), 4.70 (H-4), 2.6 (H-3),1.19 and 1.07 ppm (CH₃).

Isomer D

A mixture of Isomer D of3-(1'-p-nitrobenzyldioxycarbonyl-1'-ethyl)-1-(p-nitrobenzyl2"-chloro-2"-acetate)-4-tritylthio-2-azetidinone (4.598 g, 4.45 mmol;purity 77%, mixture of epimers at C-2"), triphenylphosphine (1.425 g,5.44 mmol; Aldrich) and 2,6-lutidine (0.63 ml, 580 mg, 5.40 mmol;Anachemia) in dioxane (65 ml; distilled from LAH) was heated at gentlereflux under N₂ for 41 h, monitoring the reaction by tlc(benzened:ether=3:1). The dark reaction mixture was cooled, diluted withEtOAc and washed successively with 0.1 NHCl, water, 2% NaHCO₃ and thenbrine. Drying (Na₂ SO₄) and evaporation of the solvents gave 4.18 g of adark coloured oil which was purified by column chromatography (SiO₂, 88g; eluent 10-25% ether in benzene), yielding 1.108 g (1.08 mmole, yield24.3%) of the title compound as a yellowish foam: .sup. 1 Hmr (CDCl₃) δ:1.08 (d, J=6 Hz, 1'-CH₃); ir (neat) ν_(max) : 1745 cm⁻¹ (s, C═O). benzyl2"-chloro-2"-acetate)-4-tritylthio-2-azetidinone was treated with2,6-lutidine (2.97 g, 3.23 ml, 27.72 mmol) and triphenyl phosphine (9.91g, 37.8 mmol). The mixture was refluxed (oil bath 130°) for 18 h. Thesolvent was evaporated and the residue was redissolved in methylenechloride. The resulting solution was successively washed with dilutedHCl, H₂ O, diluted aqueous NaHCO₃,H₂ O and brine. Drying and solventevaporation left the title compound as a solid which was triturated withether and collected by filtration (14.6 g, 65.9%); ir (CH₂ Cl₂) ν_(max): 1750 (C═O) and 1620, 1610 cm⁻¹ (phosphorane).

MM.3-(1'-Paranitrobenzyldioxycarbonyl-1'-ethyl)-1-(paranitrobenzyl-2"-triphenylphosphoranylidene-2"-acetate)-4-tritylthio-2-azetidinone.##STR112## Isomer B

A mixture of (1'R,3S,4R and 1'S,3R,4S)3-(1'-paranitrobenzyl-dioxycarbonyl-1'-ethyl)-1-(paranitrobenzyl-2"-chloro-2"-acetate)-4-tritylthioazetidinone(isomer B) (4.96 g, 6.22 mmol, mixture of epimers at C-2"), triphenylphosphine (2.47 g, 9.42 mmol) and 2,6-lutidine (740 mg, 0.80 ml, 6.91mmol) was refluxed in dioxane (freshly distilled over LAH) for 30 h. Thesolution was diluted with ether and ethyl acetate, washed with 5%aqueous HCl, water, 10% aqueous NaHCO₃, water and brine and dried(MgSO₄). Solvent evaporation afforded a

NN. Preparation of (1'S,3S,4R and1'R,3R,4S)3-(1'-Methanesulfonyloxy-1'-ethyl)-1-(pananitrobenzyl2"-triphenylphosphoranylidene-2"-acetate)-4-tritylthio-2-azetidinone(isomer C) ##STR113##

A solution of (1'S,3S,4R and 1'R,3R,4S)3-(1'-methanesulfonyloxy-1'-ethyl)-1-(paranitrobenzyl2"-chloro-2"-acetate)-4-tritylthio-2-azetidinone (24.7 g, 35.5 mmol),triphenylphosphine (11.2 g, 42.7 mmol) and 2.6-lutidine (4.2 g, 39.1mmol) in dry dioxane (350 ml) was refluxed under nitrogen for 19 h. Thesolvent was evaporated and the crude product redissolved in ethylacetate and washed successively with dilute HCl, NaHCO₃ and brine.Purification was completed by chromatography on a silica gel column(8.5×12 cm). Elution with 10% ether-dichloromethane (1.5 l) and thenether (1.5 l) gave the purified phosphorane; 12.36 g (40%). ¹ Hmr(CDCl₃) δ: 2.53 and 2.93 ppm (3H, 2s, mesylate); ir ν_(max) : 1749 and1620 cm⁻¹ (C═O).

OO. Preparation of (1'R,3S,4R and 1'S,3R,4S)3-(1'-Hydroxy-1'-ethyl)-1-(paranitrobenzyl-2"-triphenylphosphoranylidene-2"-acetate)4-tritylthio-2-azetidinone (Isomer B). ##STR114##

A solution of phosphorane (1'r,3S,4R and 1'S,3R,4S)3-(1'-acetoxy-1'-ethyl)-1-(paranitrobenzyl2"-triphenylphosphoranylidene-2"-acetate)-4-tritylthio-2-azetidinone(4.43 g, 5.00 mmol) in methanol (10 ml) THF (60 ml) was treated at roomtemperature with 1% aqueous NaOH (1 eq, 200 mg in 20 ml H₂ O). Thereaction progression was followed by tlc*. The mixture was diluted withether-ethyl acetate and washed with HCl, H₂ O, aqueous NaHCO₃, H₂ O andbrine. Solvent evaporation afforded a residue which was crystallizedfrom benzene-ether (3.7 g, 87.7%) mp 169.5°-170.5° C. ir (CH₂ Cl₂)ν_(max) : 1745 (C═O) and 1620 cm⁻¹ (phosphorane).

PP. Preparation of (1'S,3R,4R and 1'R,3S,4S) Silver3-(1'-methoxymethyl-1'-ethyl)-1-(paranitrobenzyl2"-triphenylphosphoranylidene-2"-acetate)-2-azetidinone-4-thiolate(Isomer A) ##STR115##

Silver 3-(1'-methoxymethyl-1'-ethyl)-1-(paranitrobenzyl-2"-triphenylphosphoranylidene-2"-acetate)-3-tritylthio-2-azetidinone(isomer A), was prepared as described elsewhere for the isomer C of theparanitrobenzyldioxy carbonyl derivative. Yield 50%. ir (neat ν_(max) :1745 cm⁻¹ (C═O).

QQ. Preparation of 1'S,3S,4R and 1'R,3R,4S) Silver2-(1'-methoxymethyloxy-1'-ethyl)-1-(paranitrobenzyl2"-triphenylphosphoranylidene-2"-acetate)-2-azetidinone-4-thiolate(Isomer C) ##STR116##

(1'S,3S,4R and 1'R,3R,4S)3-(1'-methoxymethyloxy-1'-ethyl)-1-(paranitrobenzyl2"-triphenylphosphoranylidene-2"-acetate)-4-tritylthio-2-azetidinone(887 mg, 1.0 mmol) was first dissolved in hot (40° C.) methanol (30 ml),treated with pyridine (103 mg, 0.105 ml, 1.3 mmol) and, after cooling,was treated with a 0.15 M methanol solution of silver nitrate (8.7 ml,1.3 mmol). The mixture was stirred for 1 h at 23° C., cooled (ice bath)and stirred for 20 min. The salt was filtered and washed successivelywith cold methanol and ether (3 times, 671 mg, 87%). ir (CHCl₃) ν_(max): 1745 (C═O), 1605 (phosphorane) and 1520 cm⁻¹ (NO₂).

RR. Preparation of Silver3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-1-(paranitrobenzyl 2"-triphenylphosphoranylidene-2"-acetate)-2-azetidinone-4-thiolate##STR117## "Isomer B"

(1'R,3S,4R and 1'S,3R,4S)3-(1'-paranitrobenzylcarbonyldioxy-1'-ethyl)-1-(paranitrobenzyl-2"-triphenylphosphoranylidene-2"-acetate)-4-trithio-2-azetidinone(1.02 g, 1 mmol) was first dissolved in CH₂ Cl₂ (3 ml) and diluted withhot (55° C.) MeOH (20 ml). The hot solution was treated first withpyridine (120 ml, 117 mg, 1.48 mmol) and a hot (55° C.) 0.15M methanolicsolution of silver nitrate (8 ml, 1.2 mmol). The mixture was stirred atroom temperature for 15 min, then at 0° C. for 2 h. It was thenconcentrated to a 10% solution on the rotary evaporator (no bath). Themercaptide was filtered and washed twice with cold (-15° C.) methanoland three times with ether. (917 mg, 100%). ir (nujol mull) ν_(max) :1745 (C═O), 1600 (phosphorane) and 1517 cm⁻¹ (NO₂).

"Isomer C"

Silver 3-(1'-paranitrobenzyldioxycarbonyl-1'-ethyl)-1-(paranitrobenzyl2"-triphenylphosphoranylidene-2"-triphenylphosphoranylidene-2"-acetate)-2-azetidinone-4-thiolate,"Isomer C", was prepared as described above for the "Isomer B"; ir(nujol) ν_(max) : 1745 (C═O) and 1600 cm⁻¹ (phosphorane).

"Isomer D"

A solution of Isomer D of3-(1'-p-nitrobenzylcarbonyldioxy-1'-ethyl)-1-(p-nitrobenzyl2"-triphenylphosphoranylidene-2"-acetate)-4-tritylthio-2-azetidinone(145 mg, 0.142 mmol) was prepared by first dissolving it in CH₂ Cl₂ (5ml), removing the CH₂ Cl₂ at 55°-60° and adding hot MeOH (4 ml). To theabove solution was added a hot solution of AgNO₃ in MeOH (0.15 M, 1.14ml, 0.17 mmol, 1.2 eq), followed by pyridine (14 μl, 0.17 mmol, 1.2 eq).The silver mercaptide started to precipitate immediately. The mixturewas stirred 2 h at room temperature and 1 h at 0°. The mercaptide wascollected by filtration and washed with ice-cold MeOH and ether,yielding 99 mg (0.11 mmol, 78%) of the title compound as a brownishsolid: ir (Nujol) ν_(max) : 1750 cm⁻¹ (s, C═O).

SS. Preparation of (1'R,3S,4R and 1'S,3R,4S) Silver3-(1'-hydroxy-1'-ethyl)-1-)paranitrobenzyl-2"-triphenylphosphoranylidene-2"-acetate)-2-azetidinone-4-thiolate(Isomer B) ##STR118##

A solution* of (1'R,3S,4R and 1'S,3R,4S)3-(1'-hydroxy-1'-ethyl)-1-(paranitrobenzyl-2"-triphenylphosphoranylidene-2"-acetate)-4-tritylthio-2-azetidinone(1 g, 1.19 mmol) in MeOH (10 ml), was treated with pyridine (124 μl,121.3 mg, 1.53 mmol) and at 10° C. with a 0.15M solution of silvernitrate in MeOH (15 ml, 2.25 mmol--or until no more precipitation of thesilver mercaptide occurred). The mixture was stirred for 1 h andconcentrated on the rotary evaporator (no bath) to approximately 10%concentration. The solvent was filtered off. The cake was washed oncewith MeOH and 3 times with ether, and pumped under high vacuum (954 mg,100%). ir (Nujol mull) ν_(max) : 3500-3400 (O--H), 1752 (C═O) 1595(phosphorane) and 1525 cm⁻¹ (NO₂).

EXAMPLE 6 (1'R,5R,6S and 1'S,5S,6 R)6-(1'-Hydroxyethyl)-2-(2-aminoethoxymethyl)penem-3-carboxylic Acid(isomer B) ##STR119## (1'R,3S,4R and 1'S,3R,4S)4-(2-Azidoethoxy)acetylthio-3-(1'-hydroxyethyl)-1-(p-nitrobenzyl2"-triphenylphosphoranylidene-2"-acetate)-2-azetidinone (Isomer B)##STR120##

To a stirred solution of (1'R,3S,4R and 1'S,3R,4S) silver3-(1'-hydroxyethyl)-1-(p-nitrobenzyl2"-triphenylphosphoranylidene-2"-acetate)-2-azetidinone-4-thiolate(Isomer B) (820 mg, 1.16 mmol) in THF (20 ml) was added at -15°(MeOH-ice bath) under N₂ atmosphere successively triethylamine (01648ml, 4.66 mmol, 4.02 eq), chlorotrimethyl silane (0.589 ml, 4.64 mmol,4.00 eq) and imidazole (81.2 mg, 1.12 mmol). The mixture was stirred atroom temperature for 18 h (overnight) and then cooled to -10°˜-15°. Tothis was added pyridine (0.220 ml, 2.72 mmol) and then a solution of2-azidoethoxyacetyl chloride (372 mg, 2.27 mmol, 1.96 eq) in CH₂ Cl₂ (20ml). It was stirred at room temperature for 1 h. After filtration of theprecipitate, the filtrate, diluted with EtOAc, was washed successivelywith 1N HCl, brine, saturated NaHCO₃ and brine, dried (Ma₂ SO₄) andevaporated yielding 748 mg an oil. This oil dissolved in wet CH₂ Cl₂ (20ml with 3 drops of water) was treated with trifluoroacetic acid (2drops) at room temperature for 30 min. The mixture was washed withsaturated NaHCO₃ and then brine, dried (Na₂ SO₄) and evaported yielding695 mg of a crude oil. This oil was purified by column chromatography(SiO₂ 15 g, eluent EtOAc:CH₂ Cl₂ =1:1) collecting 538 mg (0.739 mmol,yield 63.7%) of the title compound as a yellowish oil: ¹ Hmr (CDCl₃) δ:1.22 (d, J=6 Hz, CH₃ -1'), 5.6 (2d, H-4) and 7.3=8.4 ppm (aromatic Hs);ir (neat) ν_(max) : 3420 (OH), 2100 (--N₃), 1750 (C═O) and 1690 cm⁻¹(thioester); Rf 0.20 (CH₂ Cl₂ :EtOAc=1:1).

(1'R,5R,6S and 1'S,5S,6R) p-Nitrobenzyl6-(1'-hydroxyethyl)-2-(2-azidoethoxymethyl)penem-3-carboxylate (IsomerB) ##STR121##

A solution of (1'R,3S,4R and 1'S,3R,4S) 4-(2-azidoethoxy)acetylthio-3-(1'-hydroxyethyl)-1-(p-nitrobenzyl2"-triphenylphosphoranylidene-2"-acetate)-2-azetidinone, (Isomer B),(490 mg, 0.673 mmol) in toluene (80 ml) was heated at gentle reflux for3 h. Evaporation of the solvent in vacuo gave an oily residue which waspurified by column chromatography (SiO₂, 10 g; eluent 5-10% EtOAc in CH₂Cl₂) followed by crystallization from CH₂ Cl₂ -ether to obtain 202 mg(0.449 mmol, yield 66.8%) of the title compound as light yellowcrystals: ¹ Hmr (CDCl₃) δ: 1.35 (3H, d, J=6.5 Hz, CH₃ -1'), 2.18 (1H,br, OH), 3.2-3.9 (5H, m, --CH₂ -- and H-6), 3.9-4.5 (1H, m, H-1'),4.45-4.72-4.75-5.02 (2H, AB type, CH₂ -2), 5.02-5.25-5.35-5.57 (2H, ABtype, -CH₂ Ar), 5.62 (1H, d, J=1 Hz, H-5) and 7.42-7.65-8.13-8.28 ppm(4H, A₂ 'B₂ ', aromatic Hs); ir (nujol) ν_(max) : 3460 (--OH), 2110(--N₃), 1765 (β-lactam) and 1680 cm⁻¹ (ester). An analytical sample wasobtained by further crystallization: mp 107°-8° C. (CH₂ Cl₂ -ether uv(EtOH) λ_(max) : 264 (ε12000) and 323 mμ (ε9200); Rf 962 (CH₂ Cl₂:EtOAc=1:1); Anal.calcd for C₁₈ H₁₉ N₅ O₇ S: C 48.10, H 4.26, N 15.88, S7.13; found: C 47.81, H 4.18, N 15.00, S 7.16.

(1'R,5R,6S abd 1'S,5S,6R) 6-1'-hydroxyethyl)-2-(2-azidoethoxymethyl)penem-3-carboxylic acid (Isomer B) ##STR122##

A solution of (1'R,5R,6S and 1'S,5S,6R) p-nitrobenzyl6-(1'-hydroxyethyl)-2-(2-azidoethoxymethyl) penem-3-carboxylate (IsomerB) (180 mg, 0.400 mmol) in THF (18 ml) was mixed with ether (19 ml), H₂O (18 ml) and 10% Pd-C (180 mg). It was hydrogenated (H₂, 55 psi) atroom temperature for 2.5 h. After filtering off the catalyst the aqueousfiltrate was washed with EtOAc and lyophilized to yield 84.4 mg (0.293mmol, crude yield 73.2%) of the title compound as a crude yellowishpowder: uv (H₂ O) λ_(max) : 305.5 (ε4800) and 255 mμ (ε3800). Thispowder was purified by hplc (Waters C₁₈ Micro Bondapack Reverse Phase 30cm×10 mm; eluent 1% CH₃ CN in H₂ O) to give 44.7 mg (0.155 mmol, yield38.8%) of the title compound as white powder: ¹ Hmr (D₂ O) δ: 1.34 (3H,d, J=6.4 Hz, CH₃ -1'), 3.26 (2H, m, --CH₂ N), 3.82 (2H, m, --OCH₂ CH₂--), 3.94 (1H, dd, J_(6-1') =6.2 Hz, J₆₋₅ =1.4 Hz, H-6), 4.2-4.4 (1H, m,H-1'), 4.52-4.70-4.84-5.02 (2H, AB type, CH₂ -2) and 5.71 ppm (1H, d,J=1.3 Hz, H-5); ir (KBr disc) ν_(max) : 3420 (OH), 3000-2600 (br, CO₂H), 1765 (β-lactam) and 1575 cm⁻¹ (--CO₂ H); uv (H₂ O) ν_(max) : 306(ε5300) and 258 mμ (ε3600).

EXAMPLE 7 2-(2-Aminoethoxymethyl)penem-3-carboxylic Acid (via mercaptideintermediate) ##STR123## Ethyl 2-chloroethoxyacetate ##STR124##

A mixture of ethyl chloroacetate (24.5 g, 0.200 mol), ethyleneoxide(8.80 g, 0.300 mol) and tetraethylammonium bromide (0.40 g, 1.9 mmol;dried in vacuo) was heated in a bomb at 150°-160° C. for 6 h. Aftercooling, the reaction mixture was distilled under reduced pressurecollecting 6.66 g (54.4 mmol, 27.2%) of ethyl chloroacetate, bp 22°-24°C. (0.5 mmHg) and 8.39 g (50.4 mmol, 25.2%) of ethyl2-chloroethoxyacetate as a colourless oil; bp 49°-53° C. (0.1 mmhg); ¹Hmr (CDCl₃) δ: 1.28 (3H, t, J=7 Hz,-CH₃), 3.5-4.0 (4H, m, A₂ B₂,--CH₂CH₂ --Cl), 4.15 (2H, s, --COCH₂ O--), 4.25 ppm (2H, q, J=7 Hz,--OCH₂CH₃); ir (neat)ν _(max) : 1740 cm⁻¹ (C═O ester). Procedure of D. Klamannet al, Jastus Liebig Ann., 710, 59 (1967) (Reported: yield 42%, bp55.5°/0.35 mmHg).

Ethyl 2-azidoethoxyacetate ##STR125##

A mixture of ethyl 2-chloroethoxyacetate (7.71 g, 36.3 mmol) and sodiumazide (3.31 g, 50.9 mmol) in DMF (100 ml) was heated at 80°-90° C. for3.5 h by which time tlc (hexane; ether 1:1) indicated that the reactionwas complete. The cooled mixture was poured into H₂ O (1 l) andextracted with ether (250 ml×3). The extracts washed with H₂ O (×2) andbrine (×1) were dried (MgSO₄) and evaporated yielding 7.16 g (41.4 mmol89.4%) of ethyl 2-azidoethoxyacetate as a yellowish oil: ¹ Hmr (CDCl₃)δ: 1.30 (3H, t, J=7 Hz, --OCH₂ CH₃), 3.3-4.0 (4H, m, --OCH₂ CH₂ N₃),4.13 (2H, s, --COCH₂ O--), 4.23 ppm (2H, q, J=7 Hz, --OCH₂ CH₃); ir(neat) ν_(max) : 2100 (N₃) and 1750 cm⁻¹ (C═O ester). This material wasused in the next step without further purification.

2-Azidoethoxyacetic acid ##STR126##

To a solution of ethyl 2-azidoethoxyacetate (6.56 g, 37.9 mmol) in MeOH(80 ml) was added 1N aq. NaOH (80 ml) and the mixture was stirred atroom temperature overnight (17 h). After removing the insolublematerial, the methanol was evaporated in vacuo and this was saturatedwith sodium chloride and washed with ether (30 ml×3). The aqueous layeracidified with 3N HCl (30 ml) was extracted with ether (40 ml×4). Theether extracts were washed with brine, dried (MgSO₄) and evaporated toyield 4.25 g (29.3 mmol, 77.3%) of 2-azidoethoxyacetic acid as acolourless oil: ¹ Hmr (CDCl₃) δ: 3.3-4.0 (4H, m, --OCH₂ CH₂ N₃), 4.22(2H, s, --COCH₂ O--), 9.52 ppm (1H, s, --CO₂ H, exchanged with D₂ O); ir(neat) ν_(max) : 2600-3300 (br,--CO.sub. 2 H) 2100 (azide) and 1740 cm⁻¹C═O-CO₂ H). This material was used in the next step without furtherpurification.

2-Azidoethoxyacetyl chloride ##STR127##

A solution of 2-azidoethoxyacetic acid (2.09 g, 14.4 mmol) in thionylchloride (5 ml) was stirred at room temperature for 4 h. The excessthionyl chloride was removed under the vacuum of the water aspirator andthe residue dissolved in benzene (10 ml, dried over molecular sieves)was evaporated in vacuo. The oil so obtained was dried in vacuo (waterpump) over NaOH for 1 h yielding 2.23 g (13.6 mmol, 94.4%) of2-azidoethoxyacetyl chloride as a colourless oil: ¹ Hmr (CDCl₃) δ: 3.43(2H, br. t, J=5 Hz, --CH₂ O--) 3.78 (2H, br. t, J=5 Hz, --CH₂ N₃) and4.50 ppm (2H, s, --COCH₂ O--); ir (neat) ν_(max) : 2100 (azide) and 1800cm⁻¹ (--COCl). This material was used in the next reaction without anypurification.

4-(2'-azidoethoxyacetylthio)-1-(paranitrobenzyl2"-triphenylphosphoranylidene-2"-acetate)-2-azetidinone. ##STR128##

To a stirred solution of silver1(paranitrobenzyl-2'-triphenylphosphoranylide-2'-acetate)-2-azetidinone-4-thiolate(7.96 g, 12.0 mmol) in CH₂ Cl₂ (100 ml) containing pyridine (1.94 ml,24.0 mmol) was added at 0°-5° C. under a nitrogen atmosphere a solutionof 2-azidoethoxyacetyl chloride (2.23 g, 13.6 mmol) in CH₂ Cl₂ (20 ml)and the mixture was stirred at room temperature for 2 h. Afterfiltration of the precipitate, the filtrate was evaporated and theresidual oil was purified by column chromatography (SiO₂, 160 g; eluent,EtOAc:CH₂ Cl₂ =1:1) collecting 4.216 g (6.17 mmol, 51.4%) of the titlephosphorane as a yellowish foam. This foam was used in the next step. Ananalytical sample was obtained by crystallization from CH₂ Cl₂ -ether(1:9): mp 128°-9° C. (dec.); ir (nujol) ν_(max) : 2090 (--N₃), 1755(β-lactam) and 1690 cm⁻¹ (thioester); Anal. calcd for C₃₄ H₃₀ N₅ O₇ PS:C 59.74, H 4.42, N 10.26, S 4.69; found: C 59.33, H 4.49, N 9.69, S5.19; tlc (EtOAc) Rf=0.55.

p-Nitrobenzyl 2-(2-azidoethyl)methyl-penem-3-carboxylate ##STR129##

A solution (cloudy) of the above phosphorane (4.13 g, 6.04 mmol) intoluene (200 ml) was heated under reflux under a nitrogen atmosphere for1.5 h. After removal of the insoluble material, the solvent wasevaprated in vacuo and the residual oil was purified by columnchromatography (SiO₂, 80 g, eluent 5% ether in benzene) collecting 2.44g (6.02 mmol, 99.6%) of title compound as a yellowish oil. This oil wasused in the next step. Crystallization from CH₂ Cl₂ -ether (1:9) gave ananalytical sample: mp 88°-89.5° C.; ¹ Hmr (CDCl₃) δ: 3.35 (2H, t, J=5Hz,--OCH₂ --), 3.47 (1H, dd, J_(gem) =16 Hz, J_(trans) =2 Hz, C₆ -H),3.67 (2H, t, J=5 Hz,--CH₂ N₃), 3.85 (1H, dd, J_(gem) =16 Hz, J_(cis)=3.5 Hz, C₆ -H), 4.73 (2H, ABq, J=16, 19 C₂ -CH₂), 5.30 (2H, ABq,J=13.5, 9, --OCH₂ Ar), 5.63 (1H, dd, J_(trans) =2 Hz, J_(cis) =3.5 Hz,C₅ -H), 7.50-7.63-8.12-8.27 ppm (4H, A₂ 'B₂ ', aromatic Hs); ir (nujol)ν_(max) : 2100 (--N₃), 1785 (β-lactam) and 1695 cm⁻¹ (ester) uv (EtOH)ν_(max) : 263 mμ (ε12000), 320.5 mμ (ε9600) tlc (benzene:ether=1:1)Rf=0.60

2-(2-Aminoethoxy)methyl-penem-3-carboxylic acid ##STR130##

A solution of the above azido ester (1.62 g, 4.00 mmol) indimethoxyethane (50 ml) was mixed with ether (50 ml), H₂ O (50 ml) and10% Pd-C (1.62 g; Engelhard) and hydrogenated at room temperature (H₂:55 psi) for 2.5 h. After filtration of the catalyst, the aqueous layerwas washed with ether (50 ml×2) and then EtOAc (50 ml×1). The aqueoussolution was lyophilized to give 817 mg (3.34 mmol, 83.6%) of the titleamino-acid as a yellowish powder: uv (H₂ O) ν_(max) : 304 mμ (ε5000).This material was purified by hplc (Waters, C₁₈ Micro Bondapak ReversePhase 30 cm×10 mm; eluent 1% CH₃ CN in H₂ O) to give 432 mg (1.77 mmol,44.2%) of the title amino-acid as a white powder: ¹ Hmr (D₂ O) δ:3.19-3.9 (4H, m, --OCH₂ CH₂ NH₂), 3.54 (1H, dd, J_(gem) =16.9 Hz,J_(trans) =1.9 Hz, C₆ -H), 3.88 (1H, dd, J_(gem) =16.8 Hz, J_(cis) =3.7Hz, C₆ -H), 4.52-4.70-4.83-5.01 (2H, AB type, C₂ --CH₂ O--) and 5.77 ppm(1H, dd, J_(cis) =3.6 Hz, J_(trans) =1.9 C₅ -H); ir (KBr disc) ν_(max) :1770 (β-lactam) and 1580 cm⁻¹ (--CO₂ H); uv (H₂ O) ν_(max) : 304 mμ(ε5400), 256 mμ (ε3100).

EXAMPLE 8 2-(2-Aminoethylthiomethyl)penem-3-carboxylic Acid (viamercaptide intermediate ##STR131## 2-Azidoethyl methanesulfonate

    BrCH.sub.2 CH.sub.2 OH→N.sub.3 CH.sub.2 CH.sub.2 OMs

A solution of bromoethanol (7.5 g, 60.0 mmol) and sodium azide (5.0 g,76.9 mmol) in HMPT (30 ml) was heated at 115° C. for 2.5 h. The reactionmixture was cooled to 23° C. and diluted with CH₂ Cl₂ (100 ml). Thesolids were removed by filtration and the CH₂ Cl₂ was evaporated on therotary evaporator leaving a yellow liquid which was cooled to 0° C. andsuccessively treated with mesylchloride (5.57 ml, 72.0 mmol) andtriethylamine (10.0 ml, 72.0 mmol). The reaction mixture was stirred at0° C. for 1 h, then at 23° C. for 6 h, and poured into H₂ O (300 ml).The aqueous solution was extracted with ether (1×200 ml, 4×100 ml); theether extracts were combined, washed with 1N HCl solution, H₂ Osaturated NaHCO₃ solution and H₂ O, dried over anhydrous MgSO₄ andconcentrated on a rotary evaporator to an orange liquid which wasdistilled under high vacuum bp 95°-100° C. 0.3 torr, 5.8 g, 58.5%; ir(neat) ν_(max) : 2005 (s, N₃), 1345 (s, SO₂ -O), 1175 (m, SO₂ -O) cm⁻¹.¹ Hmr (CDCl₃) δ: 3.03 (s, 3H, OCH₃), 3.43-3.76 (m, 2H, H-2) and 4.2-4.46ppm (m, 2H, H-1).

2'-Azidoethylthioglycolic acid ##STR132##

Thioglycolic acid (3.14 g, 34.1 mmol) was treated with 1N NaOH solution(68 ml, 68.0 mmol) and the resulting solution was stirred at 23° C. for0.5 h and treated with a solution of 2'-azidoethyl methanesulfonate (5.3g, 32.1 mmol) in dimethoxyethane (15 ml). The reaction mixture wasstirred at 45° C. for 22 h, cooled to 23° C., washed with CH₂ Cl₂ (3×20ml), acidified with 6N HCl solution and extracted with CH₂ Cl₂ (7×40ml). The CH₂ Cl₂ extracts were combined, dried over anhydrous Na₂ SO₄and concentrated on a rotary evaporator to an oil which was distilledunder high vacuum bp 117°-22° C./0.27 torr, 4.2 g, 81.2%. ir (neat)ν_(max) : 2100 (s, N₃), 1708 (s, C═O) cm⁻¹. ¹ Hmr (CDCl₃) δ: 2.7-3.07(m, 2H, H-1'), 3.35 (s, 2H, H-1), 3.30-3.73 (m, 2H, H-2') and 11.81 ppm(s, 1H, COOH).

2'-Azidoethylthioacetyl chloride ##STR133##

To a solution of 2-azidoethylthio glycolic acid (3.33 g, 20.7 mmol) inCH₂ Cl₂ (50 ml) was added oxalyl chloride (3.9 ml) and DMF (one drop).The reaction mixture was stirred at 23° C. for 1.5 h and the solvent wasremoved on a rotary evaporator leaving a yellow liquid. ir(neat) ν_(max): 2100 (s, N₃), 1785 (bs, C═O). ¹ Hmr (CDCl₃) δ: 2.6-3.0 (m, 2H, H-1'),3.37-3.73 (m, 2H, H-2'), and 3.82 ppm (s, 2H, H-1).

4-(2'-azidoethylthioacetylthio)-1-(paranitrobenzyl2"-triphenylphosphoranylidene-2"-acetate)-2-azetidinone ##STR134##

A solution of silver 1-(paranitrobenzyl1'-triphenylphosphoranylidene-1'-acetate)-2-azetidinone-4-thiolate (15.7mmol) and pyridine (1.6 ml, 19.8 mmol) in CH₂ Cl₂ (200 ml) was treateddropwise (0.25 h) with a solution of 2'-azidoethylthioacetyl chloride(3.64 g, 20.3 mmol) in CH₂ Cl₂ (50 ml). The reaction mixture was stirredat 23° C. for 1.5 h and filtered; the solids were washed with CH₂ Cl₂.The filtrate and washings were combined and washed with 0.1N HClsolution, H₂ O, saturated NaHCO₃ solution and H₂ O, dried over anhydrousNa₂ SO₄ and concentrated on a rotary evaporator to an orange syrup. Acolumn chromatography (300 g of silica gel G-60, eluent; EtOAc in CH₂Cl₂, 0-40%) of crude compound gave after evaporation of solvent a whitepowder, 7.7 g, 70%. An analytical sample was obtained after arecrystallization from CH₂ Cl₂ -ether-pet. ether, mp 150°-1° C. dec.Anal. calcd for C₃₄ H₃₀ N₅ O₆ S₂ P: C 58.36, H 4.32, N 10.01, S 9.17;found: C 58.64, H 4.36, N 10.03, S 9.25. ir (KBr) ν_(max) : 2100 (s,N₃), 1750 (s, C═O of β-lactam), 1675 (s, C═O), 1655 (s, C═O), 1610 (s,aromatics), and 1440 cm⁻¹ (s, P-Ph).

paraNitrobenzyl 2-aminoethylthiomethylpenem-3-carboxylate ##STR135##

A suspension of 4-(2'-azidoethylthioacetylthio)-1-(paranitrobenzyl2"-triphenylphosphoranylidenylacetate)-2-azetidinone (4.5 g, 6.43 mmol)in toluene (375 ml) was stirred at 110° C. for 2.25 h under a nitrogenatmosphere. The reaction mixture was cooled to 23° C. and theevaporation of solvent on a rotary evaporator gave an orange syrup. Thepurification of crude material was done on a silica gel column (90 g ofsilica gel G-60, eluent: ether-pet-ether, 1:1-3:2); the pure materialwas obtained as a yellow syrup, 2.2 g, 81%). ir (neat) ν_(max) : 2100(s, N₃), 1785 (s, C═O of β-lactam), 1705 cm⁻¹ (s, C=O of PNB); ¹ Hmr(CDCl₃) δ: 2.53-2.90 (m, 2H, H-1"), 3.30-3.67 (m, 3H, HO2", H-6 trans),3.98 (ABq, J_(a-b) =14.8 Hz, 2H, H-1'), 5.32 (ABq, J_(a-b) =13.0 Hz, 2H,CH₂ -PhNO₂), 5.66 (dd, J_(H-5),H-6 cis =3.6 Hz, J_(H-5),H-6 trans =1.9Hz, 1-H, H-5), 7.58 (d, J_(Ho-Hm) =8.8 Hz, 2H, Ho PNB) and 8.19 ppm (d,J_(Hm-Ho) =8.8 Hz, 2H, Hm PNB).

2-Aminoethylthiomethylpenem-3-carboxylic acid ##STR136##

To a solution of p-nitrobenzyl 2-azidoethylthiomethylpenem-3-carboxylate(45 mg, 0.11 mmol) in dimethoxyethane (5 ml) were added ether (5 ml),water (5 ml) and 10% Pd/C (45 mg, 0.11 mmol). The reaction mixture washydrogenated at 23° C. under 45 psi of hydrogen for 3.0 h and filteredover a Celite pad. The pad was washed with water and the filtrate andwashings were combined and diluted with ether. The water phase wasseparated and washed with ether and lyophylized. The crude compound (20mg) was purified by hplc: 5 mg, 18%; ir (KBr) ν_(max) : 1765 (C═O), 1600cm⁻¹ (b, COO⁻); ¹ Hmr (D₂ O) δ: 2.70-3.00 (m, 2H, H-1"), 3.15-3.45 (m,2H, H-2"), 3.49 (dd, J_(gem) =16.8 Hz, J₆,5 trans =1.7 Hz, H-6 trans),3.85 (dd, J_(gem) =16.8 Hz, J_(6-5cis) =3.4 Hz, H-6 cis), 4.05 (ABq,J_(a-b) =14.6 Hz, 2H, H-1) and 5.74 ppm (dd, J₅₋₆ cis =3.4 Hz, J₅₋₆trans =1.7 Hz, 1H, H-5); uv λ_(max) : 307 (ε4330), 250 (ε3282).

EXAMPLE 9 2-(2-Aminoethylsulfonylmethyl) penem- 3-carboxylic Acid##STR137## para-nitrobenzyl 2-(2-azidoethylsulfinylmethyl)penem-3-carboxylate ##STR138##

A solution of p-nitrobenzyl 2-azidoethylthiomethylpenem-3-carboxylate(0.36 g, 0.85 mmol) in CH₂ Cl₂ (30 ml) was cooled to -20° C. under anitrogen atmosphere and treated dropwise (2 h) with a solutionm-chloroperbenzoic acid (0.147 g, 0.85 mmol) in CH₂ Cl₂ (90 ml). Thereaction mixture was stirred at -20° C. for 0.5 h, warmed up to roomtemperature and washed with a saturated NaHCO₃ solution and H₂ O. Theorganic solution was dried over anhydrous Na₂ SO₄ and concentrated underreduced pressure to an orange residue which was chromatographed oversilica gel (silica gel G 60; 9 g; eluent; 25% EtOAc in CH₂ Cl₂, fractionsize: 7 ml). Concentration of the appropriate fractions gave a whitesolid; 0.27 g, mp 128°-31° C., 72.6%. Recrystallization fromacetone-ether-pet-ether mixture gave an analytical sample; mp 142° C.dec; calcd for C₁₆ N₅ O₆ S₂ : C 43.93, H 3.46, N 16.01, S 14.66; found:C 43.79, H 3.44, N 16.02, S 14.63. ir (KBr) ν_(max) : 2110 (N₃), 1785(C═O of β-lactam), 1690 (C═O of PNB ester), 1600, 1560 (C═C), 1520, 1355cm⁻¹ (NO₂); uv λ_(max) ^(CHCl).sbsp.3 : 265 (ε12884), 333 (ε8764); ¹ Hmr(CDCl₃) δ: 2.95 (2H, m, CH₂ CH₂ N₃), 3.58 (dd, J_(H-6-H-6) trans =2.0Hz, J_(gem) =16.6 Hz, H-6 trans), 4.33 (center of ABq, J_(a),b =13.4 Hz,H-1'), 4.32 (center of ABq, J_(a),b =13.2 Hz, H-1'), 5.33 (center ofABq, J_(a),b =13.7 Hz, 2H, CH₂ of PNB ester), 5.75 (dd, J_(H-5-H-6) cis=3.6 Hz, J_(H-5-H-6) trans =2.1 Hz, 1H, H-5), 7.60 (d, J_(Ho-Hm) =8.8Hz, 2H, Ho of PNB ester) and 8.22 (d, J_(Hm-Ho) =8.8 Hz, 2H, Hm of PNBester).

2-(2-aminoethylsulfinylmethyl) penem-3-carboxylic acid ##STR139##

To a solution of paranitrobenzyl 2-(2-ethylsulfinylmethyl)penem-3-carboxylate (57 mg, 0.13 mmol) in dimethoxyethane (20 ml) wassuccessively added Et₂ O (10 ml), H₂ O (10 ml) and 10% Pd on charcoal(57 mg). The reaction mixture was hydrogenated under 55 psi for 1.25 hand filtered over a Celite pad. The filtrate was diluted with Et₂ O; theorganic phase was separated and the aqueous solution was washed with Et₂O (twice) and lyophylized. The crude orange powder (30 mg) was purifiedby hplc; lyophylization of appropriate fractions gave the title compoundas a white powder; 10.4 mg, 29%, uv λ_(max) ^(H).sbsp.2^(O) : 313(ε4877); ir (KBr) ν_(max) : 1720 (C═O of β-lactam) and 1590(carboxylate); ¹ Hmr (D₂ O) δ: 3.0-3.7 (5H, H-6 trans, CH₂ CH₂ NH₃ ⁺),3.90 (dd, J_(H-6-H-6) cis =3.6 Hz, J_(gem) =16.9 Hz, 1H, H-6 cis), 5.45(center of ABq, J_(a),b =13.6 Hz, H-1'), 4.50 (center of ABq, J_(a),b=13.6 Hz, H-1') and 5.8 (m, 1H, H-5).

EXAMPLE 10 Silver1-(β-Trimethylsilylethyl-2'-triphenylphosphoranylidene-2'-acetate)-2-azetidinone-4-thiolate##STR140## di-β-trimethylsilylethyl fumarate ##STR141##

To a cold (-10° C.) ether (20 ml) solution of 2-trimethylsilyl ethanol(4.73 g, 0.04 mmol) [H. Gerlach Helv. Chim. Acta 60, 3039 (1977)] andpyridine (5.66 ml, 0.07 mol), under nitrogen, was added dropwise (15min) fumaryl chloride (3.78 ml, 0.035 mol) dissolved in ether (10 ml).The black mixture was stirred five minutes at -10° C. and ten at roomtemperature. Charcoal was added and the reaction mixture filtered on aCelite pad. The filtrate was washed with sodium bicarbonate 1%-brine(1:1, 150 ml). The aqueous phase was back extracted with ether (30 ml).The ether solutions were combined, washed with brine, dried over sodiumsulfate, filtered and concentrated under reduced pressure to give abrown solid. This compound was purified on a silica gel pad (30 g, 4×5cm) with benzene (300 ml) as eluent to give an oil (4.855 g, 77%) whichsolidified on standing: mp 33°-34° C. Anal. calcd for C₁₄ H₂₈ O₄ Si₂ : C53.12, H 8.91; found: C 53.35, H 8.91. ¹ Hmr (CDCl₃) δ: 6.78 (2H, s,C═CH), 4.26 (4H, m, CH₂ -O), 1.03 (4H, m, CH₂ -Si) and 0.06 ppm (18H, s,(CH₃)₃ Si); ir (CHCl₃) ν_(max) : 1710 (C═O of ester), 1643 (C═C), 1267,1258, 862 and 840 cm⁻¹ (Si-C).

Trimethylsilylethyl glyoxylate hydrate ##STR142##

A solution of di-β-trimethylsilylethyl fumarate (37 g, 0.117 mmol) inmethylene chloride (1.1 l) was ozonized at -78° C. until a blue colorpersisted. The excess ozone was purged with nitrogen and dimethylsulfide (2.57 ml, 0.351 mol) was added. The solution was allowed togradually warm to 23° C. The reaction mixture was diluted with carbontetrachloride to 2 liters and washed with 1% aqueous solution of sodiumcarbonate (500 ml). The organic phase was dried over sodium sulfate,filtered on Celite and evaporated (˜25° C.) to dryness to give 43.9 g ofthe title compound (97%); ir (neat) ν_(max) : 3450 (--OH), 1740 (ester,1255, 860 and 840 cm⁻¹ (Si-C).

1-(β-trimethylsilylethyl2'-hydroxy-2'-acetate)-4-tritylthio-2-azetidinone ##STR143##

Trimethylsilylethyl glyoxylate hydrate (4.000 g, 11.6 mmol) and the4-tritylthio-2-azetidinone (4.8 g, 24.96 mmol) were refluxed in benzene(25 ml) through a Dean Stark condenser, under nitrogen for 24 h. Thesolvent was evaporated under a vacuum. The product was chromatographedon a silica gel column (450 g, 8.5×14.5 cm) and eluted with ethylacetate:methylene chloride (1:19) until the title compound started tocome out (˜1.5 l) and then with ethylacetate:methylene chloride (1:9, 2l). The fractions containing the title compound were combined andevaporated to dryness to give 5.415 g (89%) of the title compound. ¹ Hmr(CDCl₃) δ: 7.80 to 6.70 (15H, m, trityl), 5.23 and 4.90 (1H, 2s, H-C-O),4.50 to 4.10 (3H, m, H-3 and O-CH₂), 2.60 (2H, m, H-2), 0.95 (2H, m, CH₂-Si and 0.1 ppm (9H, s, Si-CH₃); ir (CHCl₃) ν_(max) : 3520 (--OH), 1765(C═O of β-lactam), 1740 (C═O of ester), 1595 (C-H, aromatic), 1257, 860and 840 cm⁻¹ (C-Si).

1-(β-trimethylsilylethyl2'-chloro-2'-acetate)-4-tritylthio-2-azetidinone ##STR144##

A solution of thionyl chloride (0.74 ml, 10.37 mmol) in dry THF (9 ml)was added dropwise with stirring to a solution of1-(β-trimethylsilylethyl2'-hydroxy-2'-acetate)-4-tritylthio-2-azetidinone (4.9 g, 9.37 mmol),pyridine (0.84 ml, 10.38 mmol) and dry THF (40 ml) at -15° C. under anitrogen atmosphere. The mixture was stirred at -15° C. for 2 h. Theprecipitate was removed by filtration on a Celite pad and washed withbenzene (50 ml). The filtrate was evaporated in vacuo at 30° C. Theresidue was dissolved in benzene (100 ml), treated with charcoal andfiltered through a Celite pad. Evaporation of the solvent gave a residuewhich was purified through a silica gel pad (100 g, 4.7×11cm):hexanebenzene (1:1, 400 ml), ether-benzene (1:19, 1 l). Evaporationof the pertinent fractions gave 4.64 g of the title compound (92%). ¹Hmr (CDCl₃) δ: 7.30 (15H, m, aromatic H), 5.77 and 5.43 (1H, 2s, CH-Cl),4.7 to 4.2 (3H, m, H-4 and CH₂ -O), 2.85 to 2.50 (2H, m, H-3), 1.15 (2H,m, CH₂ -Si) and 0.06 ppm (9H, s, Si-CH₃); ir (neat) ν_(max) : 1760(C═O), 860 and 840 cm⁻¹ (C-Si).

1-(β-trimethylsilylethyl-2'-triphenylphosphoranylidene-2'-acetate)-4-tritylthio-2-azetidinone##STR145##

A dioxane (20 ml) solution of the above chloroazetidinone (4.12 g,7.568) was treated with triphenylphosphine (2.209 g, 8,424 mmol) and2,6-lutidine (0.98 ml, 8.424 mmol). The mixture was refluxed for 3.5 h.The cooled solution was filtered and the white solid washed with THF.The filtrate was evaporated to dryness. The residue was purified on asilica gel column (200 g, 4×31 cm) using ethylacetate-hexane (3:7, 1 l;7:3, 1 l) to give the title phosphorane (4.836 g, 83%). ir (film)ν_(max) : 1755 (C═O), 1615 (phosphorane), 850 and 830 cm⁻¹ (Si-C). Anal.calcd for C₄₇ H₄₆ NO₃ PSSi: C 73.89, H 6.07, N 1.81; found: C 72.18, H6.08, N 1.83.

Silver 1-(β-trimethylsilylethyl2'-triphenylphosphoranylidene-2'-acetate)-2-azetidinone-4-thiolate##STR146##

1-(β-trimethylsilylethyl 2'-triphenylphosphoranylidene-2'-azetate)-2-azetidinone (7.64 g, 10 mmol) wasdissolved in ether (60 ml). An aqueous solution of silver nitrate (0.5M,80 ml, 40 mmol) was added followed by a rapid addition (1 min) of asolution of tributylamine (3 ml, 12.58 mmol) and trifluoroacetic acid(0.154 ml, 0.2 mmol) in ether (20 ml). The mixture was mechanicallystirred for 19 min. The precipitate was filtered, rinsed with ether (200ml), triturated in water (70 ml), filtered again and rinsed with ether(100 ml). The light brown solid was dried under vacuum (water aspirator10 min and pump 65 min) to give the title compound (6.42 g). ir (CHCl₃)ν_(max) : 1862 (C═O, 1630 (phosphorane), 860 and 840 cm⁻¹ (Si-C).

EXAMPLE 11 Silver 3-(1'-Hydroxy-1'-ethyl)-1-(β-trimethylsilylethyl2"-triphenylphosphoranylidene-2"-acetate)-2-azetidinone-4-thiolate##STR147## trans 3-acetyl-1-(β-trimethylsilylethyl2'-triphenylphosphoranylidene-2'-acetate)-4-tritylthio-2-azetidinone##STR148##

To a solution of diisopropylamine (0.80 ml, 5.5 mmol) in tetrahydrofuran(25 ml) at -78° C. was added n-butyl lithium (4.0 ml, 6.0 mmol) withstirring. After 3 min, a solution of 1-(β-trimethylsilylethyl2'-triphenylphosphoranylidene-2'-acetate)-4-tritylthio-2-azetidinone(3.82 g, 5.00 mmol) in tetrahydrofuran (40 ml) was added dropwise over20 min with stirring. After 2 min, 2.5 ml (25 mmol) of ethyl acetate wasadded and the solution was stirred for 10 min. The cooling bath wasremoved and 0.2M hydrochloric (58 ml) acid was added with vigorousstirring. Water and ethyl acetate were added (65 ml each), shaken andseparated. The organic phase was washed with water and saturated sodiumchloride (60 ml each), dried and the solvent was evaporated in vacuo togive the crude product, 4.1 g. The product was absorbed from methylenechloride onto 20 g of silica gel and placed (dry) on a 120 g silica gelcolumn. The column was eluted with ether/hexane 1:1 (200 ml) then withether (500 ml). Evaporation of the solvent from the appropriatefractions gave partially purified title compound, 2.17 g (53%); irν_(max) : 1755 (β-lactam and ester) and 1710 cm⁻¹ (ketone); ¹ Hmr(CDCl₃) δ: 1.67 and 1.87 peaks for ##STR149## trimethylsilyl andaromatic peaks; remainder poorly resolved.

3-(1'-hydroxy-1'-ethyl)-1-(β-trimethylsilylethyl2"-triphenylphosphoranylidene-2"-acetate)-4-tritylthio-2-azetidinone.##STR150##

A solution of the above compound (2.10 g, 2.60 mmol) in tetrahydrofuran(20 ml) was added to a slurry of sodium borohydride (160 mg, 4.3 mmol)in tetrahydrofuran (10 ml). The mixture was stirred at 23° C. for 4 h.Water (30 ml) was added followed by the slow addition of 1M hydrochloricacid until pH 3 was reached. The mixture was extracted with ethylacetate (50 ml). The organic phase was washed with 50 ml each of 0.1Msodium bicarbonate, diluted sodium chloride and saturated sodiumchloride then dried and the solvent was evaporated in vacuo to give thecrude product, 2.22 g. The product was absorbed from methylene chlorideonto 11 g of silica gel and placed (dry) on a 44 g silica gel column.The column was eluted with ether. Evaporation of the solvent from theappropriate fractions gave partially purified title compound, 1.43 g(68%); ¹ Hmr (CDCl₃): peaks around δ 1 for ##STR151## trimethylsilyl andaromatic peaks; remainder poorly resolved.

Silver 3-(1'-hydroxy-1'-ethyl)-1-(β-trimethylsilylethyl2"-triphenylphosphoranylidene-2"-acetate)-2-azetidinone-4-thiolate##STR152##

A solution of silver nitrate (1.43 g, 8.4 mmol) in water (40 ml) and asolution of pyridine (0.27 ml, 3.35 mmol) and the above phosphorane(1.35 g, 1.67 mmol) in ether (40 ml) were stirred together vigorously at23° C. for 1 h. The precipitate was collected by filtration, washed withwater and ether and dried to give crude title compound 1.24 g (100%); irν_(max) : 3420 (OH) and 1750 cm⁻¹ (β-lactam and ester).

EXAMPLE 12 (1'R,5R,6S and 1'S,5S,6R)6-(1'-Hydroxyethyl)-2-(2-aminoethoxymethyl)penem-3-carboxylic Acid(isomer B)-Alternate Procedure ##STR153## (1'R,3S,4R and 1'S,3R,4S)4-(2-azidoethoxyacetylthio)-3-(1'-hydroxyethyl)-1-(β-trimethylsilylethyl2"-triphenylphosphoranylidene-2"-acetate)-2-azetidinone ##STR154##

Trimethylsilyl chloride (1.54 ml, 11.8 mmol) was added to a stirredslurry of silver 3-(1'-hydroxyethyl)-1-(β-trimethylsilylethyl2"-triphenylphosphoranylidene-2"-acetate)-2-azetidinone-4-thiolate(isomer B) (2.48 g, 3.34 mmol), imidazole (136 mg, 2.0 mmol) andtriethylamine (1.64 ml, 11.8 mmol) in THF (60 ml) at 0° C. The mixturewas stirred at 23° for 18 h. Methylene chloride (60 ml) was added, themixture cooled to -15° C., pyridine (1.32 ml, 16.4 mmol) andβ-azidoethoxyacetyl chloride (1.43 g, 8.70 mmol) added and the mixturestirred at -15° C. for 0.5 h. Ether (60 ml), ethyl acetate (60 ml) and1M hydrochloric acid (20 ml) were added. The precipitate was removed byfiltration and the organic phase was washed with 0.1M hydrochloric acid(100 ml), 1% sodium bicarbonate (100 ml), and saturated sodium chloride.Concentration of the dried solution gave crude title compound as an oil.85%. ir ν_(max) : 1755 and 1695 cm⁻¹.

(1'R,5R,6S and 1'S,5S,6R) β-trimethylsilylethyl2-β-azidoethoxymethyl-6-(1'-hydroxyethyl)-penem-3-carboxylate (Isomer B)##STR155##

A solution of the above phosphorane (1.3 g) in toluene (200 ml) washeated under reflux for 3 h. Concentration of the solvent on a rotaryevaporator gave the crude title compound. Chromatography on silica gel(40 g) eluting with increasing proportions of ether in hexane gavecrystalline title compound, 65%. ir ν_(max) : 1760 and 1700 cm⁻¹ ; ¹ Hmrindicated contamination with a second isomer.

(1'R,5R,6S and1'S,5S,6R)-2-β-azidoethoxymethyl-6-(1'-hydroxyethyl)-penem-3-carboxylicacid (Isomer B) ##STR156##

A solution of anhydrous tetrabutylammonium fluoride (3 ml, 1.5 mmol) inTHF was added to a solution of the above ester (155 mg, 0.37 mmol) inTHF (2 ml) at 0° C. After 5 min at 0° C., water (10 ml) and ethylacetate (10 ml) were added, the mixture was acidified to pH 3 (1Mhydrochloric acid) and the phases separated. The organic phase wasextracted with 0.05M sodium bicarbonate, the aqueous extracts acidifiedto pH 3 with hydrochloric acid and extracted with ethyl acetate. Theorganic extracts were washed with saturated sodium chloride, dried,concentrated on the rotary evaporator and the residue triturated inether to give the crude title compound as a solid, 27 mg, 28%. irν_(max) : 3500, 1785, 1670 cm⁻¹ ; ¹ Hmr (CDCl₃) δ: 1.30 (3H, d, J=6.5,CH₃ -1'), 2.22 (1H, OH), 3.1-3.9 (5H, m, CH₂ and H-6), 3.9-4.4 (1H, m,H-1'), 5.60 (1H, d, J=1, H-5).

(1'R,5R,6S and 1'S,5S,6R)6-(1'-Hydroxyethyl)-2-(2-aminoethoxymethyl)-penem-3-carboxylic acid(Isomer B) ##STR157##

A solution of the above azidocompound (150 mg) in THF (15 ml), ether (15ml) and water (15 ml) was hydrogenated in a Parr shaker in the presenceof 10% Pd/C (150 mg) at an initial H₂ pressure of 60 psi. After 3 h thecatalyst was removed by filtration over Celite and the aqueous phase waswashed with ethyl acetate and lyophilized to give the crude titlecompound. Purification by hplc (Waters, C₁₈ Micro Bondapack ReversePhase) gave 46.7 mg of pure title compound identical to a previouslyprepared sample prepared by hydrogenation/hydrogenolysis of thecorresponding azido p-nitrobenzyl derivative.

EXAMPLE 13 6-Ethyl-2-(2-aminoethoxymethyl)penem-3-carboxylic Acid##STR158##

The 1-butenylacetate (about 1:1 mixture of cis and trans isomers) wasprepared according to P. Z. Bedoukian, J. Am. Chem. Soc: 66 1325(1944).

To cooled (-15° C.) I (50 ml) was added dropwise 10 ml (11 g, 78 mmoles)of CSI. The mixture was allowed to warm up gradually during 30 min. to0° C. It was cooled to -20° C. and poured carefully onto a mixture ofwater (8 ml) ice (35 g), NaHCO₃ (18.4 g) and Na₂ SO₃ (6.4 g). This wasstirred vigorously at 0° C. for 30 min., treated with pet. ether (250ml) and cooled to -40° C. The solvent was decanted and the residue wastreated with another 100 ml of pet. ether in the same way. The combinedpet. ether extracts were washed with water (30 ml) and dried (Na₂ SO₄)for recycling of I.

The aqueous phases were combined and extracted with ethylacetate (5×40ml). The extract was dried (Na₂ SO₄) and concentrated in vacuo to give7.0 g (57%) of a mixture of 28% II and 72% III, b.p. 82°-85° C. (0.01mm); n.m.r. δ (ppm, CDCl₃) 7.3 (1H,NH) 5.92 (0.72H, d, J=4.4, II-H-3),3.3 (0.28H, d, J=1.4, III-H-4),3.3 (1H, m, H-3), 2.24 (3H, s), 2.72 (2H,two q, J=7), 1.1 (3H, two t, J=7). ν_(c=o) 1775, 1755 cm⁻¹ Anal. calcd.for C₇ H₁₁ NO₃ C 53.49, H 7.05, N 8.91. Found C 53.12, H 6.93, H 8.85.##STR159##

Sodium thioacetate was prepared by addition of thioacetic acid (0.8 ml,850 mg, 11.2 mmoles) to a cooled (ice-bath) IN sodium hydroxide solution(11.2 ml) under nitrogen. This was added to a cooled solution of II andIII (1.57 g 10 mmoles) in water (5 ml) under N₂. The mixture was stirredfor 1 h at room temperature. Since an oil was separating, acetone (9 ml)was added and stirring continued for 1.5 h. The mixture was concentratedin vacuo to remove acetone and then extracted with methylene chloride.The extract was dried and concentrated in vacuo to give 1.65 g (95%) ofcrude mixture of 85% trans IV and 15% cis IV bp 105°-110° (0.02 mm), 7.1(1H,NH) 5.53 (0.24H, d, J=4.5, cis-H-4), 5.12 (0.8H, d, J=2.4 trans-H-4) 3.34 (1H, two t, J =7) 2.48 (3H) 1.9 (1H, two q, J=7) 1.15 (3H,two t, J=7. ν_(c=o) 1700,1765 cm⁻¹. Anal. calcd for C₇ H₁₁ N C 48.53, H6.40, N 8.07. Found C 48.18, H 6.47, N 7.77 ##STR160##

A mixture of IV (1.25 g, 7.2 mmole) and p-nitrobenzyl glyoxylate (1.6 g,7.5 mmole) in benzene (80 ml) was refluxed 20 h under a Dean Stark watercollector followed by concentration in vacuo to give 3.01 g of crudeproduct. This was filtered over a small amount of silica in chloroformto give 2.8 g (quantitative yield) of slightly yellow oil V containingsome solvent, δ 7.9 (4H, m) 5.3 (4H,m) 4.8 (1H, OH) 3.2 (1H, m) 3.37 and3.33 (3H, two s) 1.8 (2H, m) 1.05 (3H, m) ν_(c=o). 1765,1700 cm⁻¹. Thisproduct was used in the next step without further purification.##STR161##

To a cooled (ice-bath) stirred solution of V (2.1 g, 5.5 mmole) in drybenzene (10 ml) was added thionyl chloride (3 ml) and the mixture keptat 5° C. for 2 h followed by evaporation in vacuo at room temperature.The excess thionyl chloride was removed by repeated addition andevaporation of benzene and the product was purified by filtration of thebenzene solution over a small amount of silica gel, to give afterconcentration in vacuo 1.7 g (77%) of crude slightly yellow oil VI, δ7.9 (4H, m) 6.0 (1H, s) 5.3 (3H, m) 3.3 (1H, m) 2.7 and 2.3 (3H, two s)1.75 (3H, m) 1.0 (3H, m) ν_(c=o) 1700, 1775 cm⁻¹. The product was usedin the next step without further purification. ##STR162##

A mixture of VI (1.7 g, 4.2 mmoles), triphenylphosphine (1.57 g 6.0mmoles) and 2,6-lutidine (5.35 mg, 5 mmoles) in dry dioxane (20 ml) washeated at 55° for 19 h, followed by concentration in vacuo. The dark-redresidue was chromatographed on a silica gel column (35 g). Elution withbenzene-ether gave 2.3 g (87%) of crude VII as light red oil, which wasused in the next step without further purification. ##STR163##

Mercaptide VIII is prepared from VII by the general procedure of Example3. ##STR164##

Reaction of mercaptide VIII with 2-azidoethoxyacetyl chloride accordingto the procedure of Example 6 gives intermediate IX which may becyclized and reduced as in Example 6 to give the title product.

Biological Data

Representative compounds of the present invention were subjected to invitro antibiotic screening against a variety of microorganisms. Samplesof the indicated compounds after solution in water and dilution withNutrient Broth were found to exhibit the following Minimum InhibitoryConcentration (MIC) in mcg./ml. versus the indicated microorganisms asdetermined by overnight incubation at 37° C. by the tube dilutionmethod.

    ______________________________________                                        M.I.C. in mcg/ml                                                                          Compound (Example No.)                                            Organism      6      7         8      9                                       ______________________________________                                        Streptococcus pneumoniae                                                                    .03    .13       .13    .5                                      A9585                                                                         Streptococcus pyogenes                                                                      .03    .13       .13    .5                                      A9604                                                                         Staphylococcus aureus                                                                       .06    .13       .13    .5                                      A9537                                                                         Staph aureus +50%                                                                           .5     1         .5     4                                       Serum A9537                                                                   Staphylococcus aureus                                                                       .25    32        16     4                                       A9606                                                                         Staphylococcus aureus                                                                       1      125       16     63                                      A15097                                                                        Streptococcus faecalis                                                                      4      32        63     >63                                     A20688                                                                        Escherichia coli                                                                            .5     2         4      8                                       A15119                                                                        Escherichia coli                                                                            .5     8         16     32                                      A20341-1                                                                      Klebsiella pneumoniae                                                                       2      4         8      32                                      A15130                                                                        Klebsiella species                                                                          2      >125      >63    >63                                     A20468                                                                        Proteus mirabilis                                                                           1      2         4      8                                       A9900                                                                         Proteus vulgaris                                                                            1      8         16     16                                      A21559                                                                        Proteus morganii                                                                            4      8         8      16                                      A15153                                                                        Proteus rettgeri                                                                            2      2         8      16                                      A21203                                                                        Serratia marcescens                                                                         2      2         8      32                                      A20019                                                                        Enterobacter cloacae                                                                        8      8         32     32                                      A9659                                                                         Enterobacter cloacae                                                                        2      4         32     63                                      A9656                                                                         Pseudomonas aeruginosa                                                                      16     63        63     63                                      A9843A                                                                        Pseudomonas aeruginosa                                                                      8      125       >63    63                                      A21213                                                                        Hemophilus influenzae                                                                       --     --        --     --                                      A9833                                                                         Haemophilus influenzae                                                                      --     --        --     --                                      A21522                                                                        Bacteroides fragilis                                                                        --     --        --     --                                      A20931                                                                        Bacteroides fragilis                                                                        --     --        --     --                                      A26929                                                                        ______________________________________                                        044617271360x v

The compounds of Examples 6 and 7 were also tested in vivo in mice andtheir PD₅₀ (dose of compound in mg/kg required to protect 50% of thetreated mice against an otherwise lethal infection of a microorganism)values determined with respect to S. aureus A9537.

    ______________________________________                                                # of infecting                                                                organisms of                                                                             # of    Treat-                                                     S. aureus  treat-  ment  PD.sub.50                                    Compound                                                                              A9537      ments   route (mg/kg/treatment)                            ______________________________________                                        Compound                                                                              1.1 × 10.sup.6                                                                     2       IM    0.12                                         of Ex. 6                                                                      Compound                                                                                1 × 10.sup.6                                                                     2       IM    1.9                                          of Ex. 7                                                                      ______________________________________                                    

We claim:
 1. An intermediate having the formula ##STR165## wherein Q isphenyl or (lower)alkyl; R" is a conventional carboxyl protecting group;Alk is a C₁ -C₂ alkylene group optionally substituted by a C₁ -C₄ alkylradical; A is O, S, SO, SO₂ or NR₂₁ in which R₂₁ is hydrogen,(lower)alkyl, phenyl or phenyl(lower)alkyl; Alk' is a C₂ -C₄ alkylenegroup; R₂₀ is --NHOH, --NR₂₂ R₂₃ in which R₂₂ and R₂₃ are eachindependently hydrogen or (lower) alkyl, --N₃ or --NO₂ ; and Y is ethyl,α-hydroxyethyl and α-hydroxyethyl in which the hydroxy group isprotected by a conventional blocking group; or a pharmaceuticallyacceptable acid addition salt thereof.
 2. A compound of claim 1 whereinY is ethyl or α-hydroxyethyl.
 3. An intermediate having the formula##STR166## wherein Q is phenyl or (lower)alkyl, R" is a conventionalcarboxyl protecting group and Y is ethyl or α-hydroxyethyl.
 4. Anintermediate having the formula ##STR167## wherein Q is phenyl or(lower)alkyl, R" is a conventional carboxyl protecting group and Y isethyl or α-hydroxyethyl.